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empreinte. 

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dernidre  image  de  cheque  microfiche,  selon  le 
cas:  le  symbole  — ►  signifie  "A  SUIVRE '.  le 
symbols  V  signifie  "FIN". 

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film^s  A  des  taux  de  rMuction  diff^rents. 
Lorsque  le  document  est  trop  grand  pour  Atre 
reproduit  en  un  seul  cliche.  11  est  film6  A  partir 
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et  de  haut  en  bas,  en  pranant  le  nombre 
d'images  n^cessalre.  Les  diagrammes  suivants 
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LI 


i     ■ 


,'.:''>:- 


AN 


INTRODUCTION 


TO  THE  STUDY  OF 


QUALITATIVE  CHEMICAL 


ANALYSIS. 


BV^ 


LAUNCELOT  WINCHESTER  ANDREWS,  M.A.,  Ph.D.,  etc., 

PROFESSOR  OF  CHEMISTRY 

AND  DIRECTOR  OF  THE  CHEMICAL  LABORATORIES 

AT  THE  STATE  UNIVERSITV  OF  IOWA. 


1 


ri" 


>^  COPYRIGHT- ''«'.$> 

IViAY.'35  189!" 


a.*" 


A.  J.  HERSHIRE  AND  COMPANY. 
I  89  I. 


MfTiillWi 


■i 


.^." 


;-.'^ 


■} 


Copyright,  1891, 
By  Launcelot  Andrews, 

All  Riffhts  Reserved. 


.A*(rS<'»Btii.v..*^'"6'-^'5^*^'">'- 


i . 


PREFACE, 


The  object  of  this  work  is  to  present  to  college  students  the  main 
facts  and  methods  of  Qualitative  Analysis  with  the  fullness  requisite  for 
successful  study,  but  in  a  form  simplified  by  the  omission  of  the  rarer 
elements,  and  more  condensed  than  that  in  which  they  are  given  in 
the  classical  Manual  of  Fresenius.  ;    '  ' 

Believing  that  the  study  of  this  branch  should  always  be  preceded  by 
theoretical  and  practical  instruction  in  General  Chemistry,  an  elementary 
acquaintance  with  that  science  is  assumed.  Nevertheless,  all  the  more 
important  quaUtative  reactions  are  elucidated  by  chemical  equations, 
and  but  Uttle  knowledge  is  taken  for  granted,  beyond  that  which  a 
comprehension  of  the  symbols  and  of  the  nomenclature  implies.  The 
nomenclature  adopted  is  in  harmony  with  the  recommendations  of  the 
Chemical  Society  of  London  and  of  the  Committee  on  Nomenclature 
of  the  American  Chemical  Society,  except  in  one  riinor  point. 

It  is  hoped  that  the  scheme  for  the  systematic  detection  of  the  acid 
radicals,  which  offers  some  novel  features,  will  be  found  elsewhere  as 
practical  and  useful  as -an  experience  of  some  years  has  shown  it  to 
be  at  this  laboratory.  The  aim  throughout  has  been  to  discourage, 
so  far  as  possible,  the  pernicious  habit  of  working  in  a  mechanical 
way  by  rul?  of  thumb,  and,  for  this  reason,  analytical  tables  have  been 
excluded,  with  the  exception  of  tables  for  the  blowpipe  examination  of 
metallic  and  i.on-metallic  substances,  to  which  the  suggested  objection 
does  not  apply  and  which  have  been  elaborated  with  especial  care. 

Numerous  cross-references  have  made  it  possible  to  avoid  many 
repetitions,  which  without  them  would  have  been  necessary,  and  will 


-jm 


^jjrT-r-~: .  ■  ■^-  ^I'T'^tJMMr  »««*^ 


iv 


PREFACE. 


be,  it  is  thought,  in  conjunction  with  copious  rnargiiial  notes,  a  welcome 
feature  to  all  those  who  may  have  occasion  to  use  this  book  in  the 
laboratory. 

The  author  desires  to  express  his  acknowledgements  to  Mr.  F.  W. 
Spanutius,  M.  Sc,  Instructor  at  this  University,  for  valued  assistance  in 
the  preparation  of  the  manuscript  and  in  testing  certain  methods,  and 
to  Mr.  E.  W.  Rockwood,  A.  M.,  Demonstrator  in  the  Medical  Depart- 
ment, for  suggestions  relative  to  the  blowpipe  analysis  of  alloys. 

Cliemical  Laboratory, 

State  fjnivenity  of  Iowa, 
Feb.  ajil,  jSgi. 


!   1 


■'*te 


--«rMw*w»?-:«»nn-.^'.^«;ww»-*»!3sv*sffi*' 


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il  notes,  a  welcome 
le  this  book  in  the 

lents  to  Mr.  F.  W. 
iralued  assistance  in 
irtain  methods,  and 
he  Medical  Depart- 
lysis  of  alloys. 


i*,'t 


CONTENTS. 


-^    CHAPTER   I. 

METHODS  AND  MANIPULATIONS. 

Introductory. 

Scope  and  Method  of  Qualitative  Analysis, 
Operations  and  Reactions. 

Flame  Tests, 

Blowpipe  Reactions,         .        .        .        • 
.;r,   ?  Use  of  the  Closed  Tube,       .        .        .        . 

v?3'    '  Use  of  the  Open  Tube,     .... 

f  Solution  and  Precipitation, 

'   .  ->  Filtration, 

Evaporation  and  Crystallization, 
'-':'-'' •:\-'''-'         Use  of  Test  Papers, 

■:v-vj:;,4;;..  ■..:.;a-:-\:.;;.;,'  chapter  II. 

REACTIONS  OF  THE   BASES. 


Analytical  Classification,     .  . 

Group  I :     . 

Sodium, 

Potassium, 

Ammonium, 

Group  II:    .  .    ,^ 

Calcium, 
Strontium, 
Barium, 
Magnesium, 

Group  III:     .        .        .        • 
Aluminium, 
Chromium,    . 

Group  IV: 

Cobalt,    . 
Nickel,       . 
Iron, 


i    1-6 

7 

8-13 

»4 

15 

16,17 

18,19 

20 

31-34 


35 
36 

37-30 

3«-35 
36-40 

41,42 

43-46 

47-50 

51-55 

56-61 

63 

63-67 

68-73 

74 

75-80 

81-86 

87-100 


mmmam 


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5  I 


*■  ,■■* 

CONTENTS. 

Manganew 9§'0'-'o8 

Zinc '°9-"' 

Group  V : ■* 

Silver 'M-'^o 

Mercury '"-"^ 

Lead "9-.3S 

Copper '30-146 

BUmuth, «47-«S4 

Ciidtnlum, '^"^"''o 

Group  VI: ,       '^8 

Tin '59-.6S 

Arsenic, '6'^-' 73 

Antimony '74-iJo 

Platinum '     . 

Gold, •        .        .        .  1S4-187 

CHAPTER   III. 

RRACTION8  OF   THB   ACIDS. 
^,01.  ...  188 

General  RcmarkB, 

Analytical  Classification, '  '^ 

Group  I: 

Sulphate '5°-'93 

Group  II: 

Division  I : -' ' 

Sulphites •y5->9S 

Carbonates ' '^9-202 

Ox.ilate8 ='°-5-2o6 

Fluorides 207-209. 

310 

Division  2: 

Phosphates,  311-214 

Arsenates =*'S-2«8 

Chromates, 219-231 

Borates, 223-227 

Silicates, "8-333 

Group  III: 

Division  I : ^ 

Sulphocyanates,     .        .        •        •        •        ■        *-       •  '35i  ^2P 

Ferrocyanides,  2.^7-239 

Ferricyanldes, 240,  -41 

Division  2: 

Nitrites, 242-=^4^ 

Hypochlorites 246-248 

Chlorltcs ='^y'2S0 

Free  Haloids 3si-2.«;9 

260 

Division  3: ^    ,*, 

Sulphides ;        •  =»6i-263 

Polysulphides, ^°* 

Thiosulphates, 265-268 


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108 

.  109- 

113 

, 

"3 

.  JI4- 

120 

lai- 

128 

.   139- 

135 

136-146 

■  147- 

»54 

155- 

157 

158 

159-165 

.  166- 

■'73 

»74- 

-I  So 

.  181- 

-183 

.   .    .84- 

-187 

188 
189 

i9«>-i93 

'94 
195-198 
1 99-202 
203-206 
307-209  • 

3IO 
211-214 

215-21S 
219-222 
223-237 
228-233 

234 
335.  336 
237-339 
240,  241 

243-245 

246-248 

249,  250 

251-259 

260 

,      261-263 

264 

.      365-268 


CONTENTS. 

Dlvl.Ion  4 : W        »^ 

ChloHtlen 270-272 

Bromide*,            .        .                373-375 

Ioclldi.» 376-281 

Cyanides, 282-384 

Group  IV: 

Tartrates, 385-388 

Group  V: '89 

Acetntcs 390,391 

NitiatfH 392-396 

Chloraten 397-30O 

CHAPTER    IV. 

SYSTEMATIC    ANAI-YSIb. 

PreHmlnary  Examination, 3oi 

Blowpipe  Tests 303-304 

Sulphuric  Acid  Test, 305 

Detection  of  the  Acids, 3o6 

Group  1 307 

Group  II,       .        .                3o8-3'i 

Group  III, 3'3-3i9 

Group  IV, 330 

Group  V 331 

Detection  of  the  Bases, 333,  333 

Separation  of  Groups  V  and  VI  from  Lower  Groups,  334 

Separation  of  the  Fifth  from  the  Sixth  Group,  335 

Group  VI, 336 

Group  V 337-339 

Groups  I,  II,  III,  and  IV, 330-347 

Examination  of  Insoluble  Substances 34^-359 

Analysis  of  Silicates, 357 

Removal  of  Organic  Matter, 3^0 

CHAPTER  V. 

"\        .  SPECIAL  PART. 

Analysis  of  Potable  Water, 36- "377 

Normal  and  Abnormal  Constituente,  363-364 
InterpreUtion  of  Results,     ......  37^ 

Analysis  of  Alloys,    .        .       , 379-385 

PAGE 

Atomic  Weights  and  Quantivalence  of  the  Elements,         ...  103 

Synopsis  of  Blowpipe  Reactions  of  Metals 104 

Synopsis  of  Blowpipe  Reactions  of  Non-metallic  Substances,     .        .  105 

Table  of  Solubilities •        •  106-109 

Explanation  of  Signs  to  Table  of  Solubilities, no 

Table  of  Reagents,     .        . m,  lU 

Index f       • "3-"5 


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CHAPTER  I, 


METHODS  AND  MANIPULATIONS  OF 
QUALITATIVE  ANALYSIS. 


INTRODUCTORY. 

1.  The  object  of  qualitative  analysis  is  to  ascertain  what 
constituents  are  present  in  any  mixture.      But  few  of  the 
compounds  of  carbon,  or  organic  substances,  are  ordinarily  ^''J^*^*' 
included,  because  a  search  for  them  would  entail  too  much 
complication  in  the  processes. 

2.  The  means,  by  which  inorganic  substances  are  identi- 
fied, vary  according  to  the  nature  of  the  substance.  Some  of 
the  elements  will  impart  a  characteristic  color  to  the  non- 
luminous  flame,  others  may  be  converted  into  compounds  Method 
having  an  appearance  which  can  be  readily  recognized,  or 
again  others  may  give  rise  under  certain  conditions  to  distinc- 
tive odors.     Any  such  phenomena,  which  may  be  utilized  for 

the  identification  of  an  element  or  a  chemical  compound,  are  Reactions, 
known  as  its  reactions. 

3.  Very  often  the  reactions  of  one  substance  will  interfere 
with  those  of  another,  for  example,  sodium  will  impart  to  the 
non-luminous  flame  a  yellow  coloration,  calcium  an  orange; 
therefore,  neither  of  these  substances  can  be  recognized  by 
the  flame  test  when  the  two  are  mixed  together.  In  such 
cases  it  is  necessary  to  separate  those  constituents  whose 
reactions  mutually  interfere. 


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METHODS  AND  MANIPULATIONS. 


[§7 


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4.  The    practice    of  qualitative    analysis   is   accordingly 

divided  into  two  distinct  parts,  namely:  first,  separation  into 

groups  of  substances  of  such  a  character  that  the  members  of 

each  group  will  not  interfere  with  the  reactions  of  other  mem- 
Separation  or 

of  constit-  ^^'"8  o^  t^^  same  group :  second,  identification  of  the  individual 
uents.        members  of  each  group.     Now,  it  is  often  impossible  that  the 
identification  can  be  positive  and  conclusive,  unless  the  separa- 
tion has  been  complete. 

5.  The  student  should  always  bear  in  mind  that  the  first 
steps  of  an  analysis,  looking  to  a  separation,  are  just  as  impor- 
tant as  the  last,  and  that  success  can  only  be  attained  by  a 
conscientious  attention  to  detail,  from  beginning  to  end.  The 
reactions  of  a  substance  are  often  displayed  by  the  addition  to 
the  body  under  examination  of  some  material  which  may  be 

Reagents,  either  solid,  liquid,  or  gaseous,  and  which  is  called  a  reagent. 
It  is  a  frequent  error  of  beginners  to  employ  too  large  a  quan- 
tity both  of  the  substance  under  examination  and  of  the  rea- 
gent. In  most  cases,  a  drop  is  as  good  as  a  test  tube  fuU, 
and  the  employment  of  too  large  quantities,  or  too  concen- 
trated solutions,  is  hkely  to  delay  the  work,  and  sometimes,  to 
obscure  the  reaction. 

6.  The  order  in  which  the  tests  are  applied  for  the  detec- 
tion of  the  constituents  of  a  mixture  is  by  no  means  a  matter 
of  indifference.  The  system,  which  experience  has  developed: 
and  which  is  here  laid  down,  for  the  guidance  of  the  student, 
is  that  which  will  most  quickly  lead  to  reliable  results,  and  the 
learner  should  not  undertake  to  depart  from  it. 


OPERATIONS    AND    REACTIONS,  j^ 

FLAME   TESTS. 

7.  In  most  chemical  operations  the  flame  of  a  Bunsen 
burner  is  employed  as  a  source  of  heat. 

This  instrument  is  so  constructed  as  to  bum  a  mixture  of 
gas  and  air.  The  flame  should  be  of  a  clear,  pale  blue.  If  it 
emits  any  yellow  light,  the  burner  is  out  of  order.  A  careful 
inspection  of  this  flame  shows  that  it  consists  of  three  pants. 

The  interior  portion  (Fig.  i),  a,  is  a  cold  mixture  of  gas 


System. 


Bunsen 
flame. 


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lysis  is  accordingly 
first,  separation  into 
that  the  members  of 
ctions  of  other  mem- 
tion  of  the  individual 
n  impossible  that  the 
;e,  unless  the  separa- 

in  mind  that  the  first 
on,  are  just  as  impor- 
tily  be  attained  by  a 
ginning  to  end.  The 
ed  by  the  addition  to 
aterial  which  may  be 
ch  is  called  a  reagent. 
ploy  too  large  a  quan- 
lation  and  of  the  rea- 
d  as  a  test  tube  fuW, 
itities,  or  too  concen- 
jrk,  and  sometimes,  to 

applied  for  the  detec- 
by  no  means  a  matter 
perience  has  developed: 
uidance  of  the  student, 
-eliable  results,  and  the 
from  it. 

\CTIONS~  ,J 

le  flame  of  a  Bunsen 

IS  to  bum  a  mixture  of 
a  clear,  pale  blue.     If  it 
,ut  of  order.     A  careful 
onsists  of  three  pants. 
)  a  cold  mixture  of  gas 


-,.-,.  ..;         ■"*-,- 


^TMHgftir^' 


nMMWHIIimiMiiiMliii- 


!  r 


o- 


uj 

cvi  N 

o 

I 


Id 
d 

(a 

I 


1* 


§7] 


FLAME   TESTS. 


UJ 

m 

Q 
l«J 

I 


U) 


i 


and  air.  This  is  immediately  surrounded  by  a  blue  cone,  6. 
In  this  layer  most  intense  combustion  is  taking  place.  It  is 
known  as  the  zone  of  reduction  or  deoxidizing  jlame^  because 
here  the  coal  gas  is  present  in  excess  as  compared  with  the 
air.  Immediately  surrounding  this  portion  of  the  flame  is  a 
somewhat  thicker  zone,  which  may  be  called  the  zone  of 
fusion  or  outer  reducing  flame.  Outside  of  this  is  a  layer 
which  emits  so  little  light,  that  it  can  only  be  easily  seen  in  a 
darkened  room. 

This  outer  layer  is  called  the  mantle  or  the  oxidizing  flame. 
Here  oxygen  is  present  in  excess.  Many  substances  when 
held  in  this  portion  of  the  flame  become  oxidized.  Take  a 
copper  wire  (about  No.  i6)  and  hold  it  across  the  flame  at  the 
point  c.  Observe  that  it  becomes  coated  with  a  black  layer 
of  copper  oxide.  Now  depress  it  to  a  point  marked  d  and 
observe  that  here  the  black  coating  of  copper  oxide  disap- 
pears, giving  place  to  a  bright  surface  of  metallic  copper. 

By  holding  the  wire  successively  in  different  portions  of  the 
flame,  you  will  readily  ascertain  which  parts  are  oxidizing  and 
which  are  reducing  in  their  action. 

Next  take  a  fine  platinum  wire  and  hold  it  across  the  flame 
in  different  positions.  Where  the  wire  glows  most  brightly 
the  flame  is  the  hottest.  Find  out  in  this  way  for  yourself 
where  the  hottest  portion  of  the  flame  is  and  always  use  this 
pan  of  the  flame  when  the  highest  attainable  temperature  is 
desired.  Many  substances  when  brought  into  this  portion  of 
the  flame,  d.,  will  impart  to  the  latter  a  coloration  (vide  §302). 

If  a  platinum  wire  be  drawn  through  the  fingers  and  then 
held  in  the  flame,  the  later  will  emit  a  yellow  light,  due  to  the 
sodium  existing  in  the  perspiration  which  adhered  to  the 
platinum  wire. 

The  platinum  wire  employed  for  flame  reactions  must  be 
scrupulously  clean.  It  is  a  good  plan  to  keep  it  in  a  test  tube, 
immersed  in  hydrochloric  acid  and,  before  using  it,  to  hold  it  in 
the  flame  until  it  ceases  to  color  the  latter.  The  wire  should 
frequently  be  rubbed  with  wet  sand. 


Reducing 
flame. 


Oxidizing 
flame. 


M 


Zone  of 
fusion. 


Care  of 
Pt.  wire. 


",*SCs, 


METHODS  AND  MANIPULATIONS. 
BLOWPIPE  REACTIONS. 


[»" 


8.  By  the  use  of  the  blowpipe,  a  hotter  flame  and,  conse- 
quently, a  more  intense  oxidizing  or  reducing  action  can  be 
obtained  than  with  the  Bunsen  flame.  When  the  blowpipe  is 
to  be  employed,  turn  off  the  air  supply  at  the  base  of  the 
burner  and  diminish  the  flame  to  a  height  of  about  an  inch 

Use  of  the  and  a  half. 

blowpipe.       To  produce  an  oxidizing  flame,  place  the  blowpipe  nozzle 

just  above  the  tube  of  the  burner  and  half  way  across  the 

flame.     In  this  position,  a  steady  blast  will  give  a  fine  pointed, 

blue,  oxidizing  flame.     (Fig.  2.) 

To  produce  a  reducing  flame  the  nozzle  should  be  held  just 

outside  the  flame  and  the   blast   should  be   less   powerful. 

(Fig.  3-) 

9.  Many  substances  dissolve  in  fused  borax,  imparting  to 
it  a  characteristic  coloration.  A  somewhat  stouter  platinum 
wire  than  that  which  is  used  for  flame  tests  (§7)  forms  the 
best  support  for  the  melted  borax.  For  this  purpose  the  wire 
is  bent  around  the  point  of  a  pencil  so  as  to  make  a  closed 
loop,  or  eye,  one-tenth  of  an  inch  in  diameter.  If  the  hot  loop 
be  plunged  into  powdered  borax  and  then  held  in  the  blow- 
pipe flame  (at  c.  Fig,  %)  the  borax  will  fuse  to  a  globule  of 
colorless  transparent  glass,  known  as  the  borax  bead. 

To  test  the  behavior  of  any  body  to  the  borax  bead,  it 
should  be  finely  powdered  and  touched  with  the  red-hot,  soft 
bead.  Some  of  the  substance  will  adhere  to  the  bead,  so  that 
when  the  latter  is  again  fused,  solution  will  take  place.* 

10.  The  soda  bead  is  made  and  used  in  the  same  way, 
except  that  sodium  carbonate  takes  the  place  of  borax. 

11.  The  microcosm ic  sali  bead  is  made  in  a  similar  way, 
by  fusing  sodium  ammonium  orthophosphate,  NaNHiHPO*, 
on  the  wire  loop.     Under  the  influence  of  a  high  temperature 

phosphate    ,  •         ,    „  r  ,.  ,         , 

bead         *"^  "  microcosmic  salt     forms  sodium  metaphosp/iate, 

NaNHiHPO*  =  NaPOg  +  HjO  +  NH3 


Borax 
bead. 


Soda 
bead. 


Meta- 


1  r 


>  Applications  of  this  test  are  described  in  §§78,  106,  88.  The  student  should 
practice  with  a  bead  containing  a  little  Mn,  until  he  can  make  it  colorless  in 
the  reducing  flainc  and  violet  in  the  oxidizing  flame.  .  , .    . 


1 

id 


,*«;/-r;j*fer,asE^ij«.£5;^Ksr«5®w!^5siTi^^^^^^^ 


T 


'•5. 


M" 


r  flame  and,  conse- 
cing  action  can  be 
hen  the  blowpipe  is 
at  the  base  of  the 
it  of  about  an  inch 

he  blowpipe  nozzle 

lalf  way  across  the 

give  a  fine  pointed, 

should  be  held  just 
be   less   powerful. 


borax,  imparting  to 
lat  stouter  platinum 
tests  (§7)  forms  the 
his  purpose  the  wire 
as  to  make  a  closed 
iter.    If  the  hot  loop 
;n  held  in  the  blow- 
iuse  to  a  globule  of 
borax  bead. 
)  the  borax  bead,  it 
with  the  red-hot,  soft 
e  to  the  bead,  so  that 
ill  take  place.  ^ 
ed  in  tlie  same  way, 
lace  of  borax, 
de  in  a  similar  way, 
phate,  NaNHiHPO*. 
if  a  high  temperature 
Uafhospliate, 
jO  +  NHs 

36,  88.     The  student  should 
le  can  make  it  colorless  in 


§'4] 


BLOWPIPE  REACTIONS. 


In  the  latter,  almost  all  compounds,  except  silica,  dissolve  to  a 
clear,  sometimes  colored,  glass  (§106). 

12.     Compounds  of  many  metals  wher  'used  in  the  reduc-  j^^j^^jj^jj, 
ing  flame,  on  charcoal,  either  alone  or  with  sodium  carbonate,  ^^  ^har- 
are  reduced  to  the  metallic  state.  ^     The  compound,  in  fine  coal, 
powder,  is  well  mixed  with  about  twice  its  bulk  of  sodium 
carbonate  and  enough  water  to  form  a  stiff  paste,  which  is 
placed  in  a  slight  hollow  in  the  prepared  charcoal  stick,^  and 
patiently  fused  in  a  strong  reducing  flame. 

The  product  is  to  be  removed  from  the  charcoal  and  rubbed 
with  a  little  water  to  dissolve  the  sodium  carbonate.  If  any 
metal  has  been  reduced,  it  may  be  found  in  the  undissolved 
residue  in  the  form  of  globules,  spangles  or  powder,  according 
to  the  nature  of  the  metal,  and  it  may  be  examined  as  to 
hardness,  color,  magnetic  properties,  etc.  These  characteris- 
tics are  often  sufficient  for  identification.  The  soft,  blueish 
globules  of  lead,  the  brilliant  white,  malleable  ones  of  silver, 
the  yellow  ones  of  gold,  or  the  irregular  magnetic  particles 
of  iron  or  magnetic  spangles  of  nickel,  may  for  example  be 
certainly  recognized. 

13.  Some  bodies  when  heated  alone  on  charcoal  in  the 
oxidizing  or  reducing  flame  produce  an  incrustation  or  fibn  on 

the  charcoal.     Such  films  present  characteristic  differences  of  ^'^'"*- 
appearance,  as  color  when   hot  or  cold,  distance  from  the 
heated  object,  etc.     Some  of  these  films  are  described  under 
Tin,  Lead,  Bismuth,  Arsenic,  Mercury,  etc. 

14.  Volatile  substances  when  heated  in  a  matrass,  or  hard 

glass  tube,  about  three  inches  long  by  three-tenths  of  an  inch  ^'*["*\ 
in  diameter,  are  sublimed,  forming  a  deposit  upon  the  cooler  ^^^ 
part  of  the  tube;  and  some  compounds  give  off  a  gas  when 
heated  in  the  same  way.     Among  the  bodies  which  may  be 


'K«*§§304,  135- 

•A  piece  of  ordinary  soft  wood  charcoal  may  be  used  if  the  prepared  char- 
coal is  not  at  hand.  Sometimes  it  is  desirable  to  use,  instead  of  sodium 
carbonate,  a  flux  composed  of  three  parts  of  sodium  carbonate,  two  parts  of 
potassiuni  cyanide  and  one  part  of  borax.  The  materials  should  be  fused 
together  and  powdered  for  use. 


*," 


■§ 


1^ 


Si 


'iij 


lli. 


U  i 

■111 


81 


METHODS  AND  MANIPULATIONS. 


[»'4 


Matraw,    recognized  by  their  behavior  when  heated  in  the  matrass  are 


or  clo«ed   ^q  ^jg  noted  the  following: 
tube 


Water:     ....     Appears  in  drops  or  as  a  mist  in  the 

matrass. 
Ammonium  salts:        White  sublimate,  often  odor  of  NHg 

evolved  (§37)' 
Arsenic:     ....    Shining  gray-brown  or  black  mirror. 
Some  SALTS  AND  AM AL- Minute   globules   of    mercury,   which 
GAMS  OF  mercury:        when   rubbed   with  a  copper   wire 
Mercuric  oxide:     .        moistened  with  nitric  acid,  give  it  a 

silvery  coating  (§127). 

Mercurous  chloride:  Sublimes  white,  without  fusion. 
Mercuric  chloride:  Fuses  and  sublimes,  yellow  when  hot, 

white  when  cold. 

Antimonous  oxide:    Fuses  to  a  yellow  liquid,  sublimes  as 

needle-shaped  crystals. 

Sulphur  and  some     Non- crystalline    sublimate,    brownish 
sulphides:     .     .     .         yellow    when    hot,    canary -yellow 

when  cold. 
Arsenic  and  arse-    Sublimate  dark  red  when  hot,  yellow- 
Nous  sulphides:     .        ish  red  when  cold. 
Mercuric  sulphide:    Sublimate  dull  black.  ^  ;,' 

Iodine:     ....       Black,  crystalline  sublimate,  violet  va- 
pours and  peculiar  odor. 

Some  nitratss  and     Brown  vapours  of  an  acid  reaction  and 

peculiar  odor  (§295). 

Colorless  gas  of  acid  reaction,  etches 

the  glass. 
Cyanogen  gas  evolved;  has  peculiar 

odor,  and  burns  with  crimson  flame. 

CO2  evolved;  renders  turbid  a  drop  of 

lime  water  (§199)-  f  f 


nitrites:     .     .     . 
Some  fluorides:    . 

Some  cyanides:    . 

Some  carbonates: 


^ 


■!;,mssi^iim»MSiMiik---^-^:^-'-*''^''  •' ' 


■a«iSSKBBa9J»S»iaBr 

I 


T 


7*^T/T 


vs.  [%ii 

d  in  the  matrass  are 

or  as  a  mist  in  the 
often  odor  of  NHs 

n  or  black  mirror. 

of  mercury,  which 
vith  a  copper  wire 
nitric  acid,  give  it  a 

without  fusion. 

;s,  yellow  when  hot, 

I. 

I  liquid,  sublimes  as 

rystals. 

sublimate,    brownish 
hot,    canary  -  yellow 

;d  when  hot,  yellow- 
)ld.  .  ^ 

ck. 

sublimate,  violet  va- 
liar  odor. 

:  an  acid  reaction  and 

§295). 

acid  reaction,  etches 

volved;  has  peculiar 
3  with  crimson  flame. 

ders  turbid  a  drop  of 
99).   ■  V 


0:' 


§'6] 


SOLUTION  AND  PRECIPITATION. 


»? 


Some  sulphates 
AND  sulphites:     . 

Peroxides,   chlo- 
rates, BROMATES, 
lODATES,  CHROMATES: 


SOj  evolved,  which  has  acid  reaction 
and  peculiar  odor  (§§194-198). 

Oxygen  evolved;  a  glowing  splinter  of 
wood  thrust  into  the  mouth  of  the 
tube  burns  brilliantly. 


sulphides :    .     . 

Arsenic  and  arsen 
ides:     .... 

Antimony  :     .     . 


■'--'i?. ,  .vvjiiaffwwinwiliii^ii,  L.  1 


15.  Some  substances,  which  give  no  sublimate  or  gas  in 
the  matrass,  are  oxidized  when  heated  in  a  hard  glass  tube, 
four  inches  long,  open  at  both  ends. 

The  tube  is  held  at  a  slope  of  45",  the  substance  being  placed 
in  it  at  one-third  of  the  way  from  the  lower  end  and  gradu- 
ally heated.  When  treated  in  this  way  the  following  bodies 
give  characteristic  reactions. 

Sulphur  and  some 

SOa  is  given  off  (§§194-198). 

Sublimate  of  brilliant  octahedral  crys- 
tals of  AsjOs  {vide  §§166  et  seq). 

Non-crystalline  sublimate  of  SbaOs  and 
SbjO^  {vide  §i74)- 

Bismuth:    ....     Sublimate  near  the  substance,  fusible 

to  brown  globules. 

Mercuric  sulphide  :    Sublimate  of  mercury,  SOj  being  evol- 
ved at  the  same  time. 

SOLUTION   AND   PRECIPITATION. 

16.  Most  substances  if  left  in  contact  with  water  will  dis- 
solve to  a  greater  or  less  extent.  Those  substances  which 
require  a  relatively  very  large  amount  of  water  for  their  solu- 
tion are  called  insoluble,  those  which  dissolve  more  freely  are 
termed  soltible.  SoiuWHtv 

No  absolute  line  can  be  drawn  between  soluble  and  insoluble 
substances.  Barium  sulphate,  which  will  dissolve  in  87,000 
times  its  weight  of  water,  is  commonly  termed  insoluble;  while 
calcium  sulphate,  which  dissolves  in  400  times  its  weight,  is 
termed  difficultly  soluble.  When  a  solvent  has  taken  up  all 
that  it  will  of  a  substance,  the  resulting  solution  is  said  to  be 
satwated.  '    ?• 


I     iA 


Hi 

i 

\ 


■  '  p^' 


II!  I 


i 


lii 


t 


ill 


r 


li 


8 


METHODS  AND  MANIPULATIONS. 


r§<9 


Predpita. 
tion. 


Suspend- 
ed precipi 
tales. 


Effect  of 
dilution. 


Filtration. 


Washing 
of  precipi- 
tates. 


Tests  for 
comple- 
tion of 
washing. 


The  limit  of  saturation  depends  upon  the  temperature. 
Almost  all  substances  are  more  soluble  at  higher  than  at 
lower  temperatures. 

17.  When  two  solutions  are  mixed  together  and  produce, 
by  chemical  change,  an  insoluble  compound,  the  latter  will 
appear  as  a  -precipitate.  Most  precipitates,  if  abundant,  will 
soon  settle  to  the  bottom  of  the  solution,  leaving  the  latter 
clear.  If  the  precipitate  is  in  very  small  quantity  or  in  a  very 
fine  state  of  division,  it  may  remain  suspended  for  a  long  time 
in  the  solution,  and  will  then  only  appear  as  an  opalescence. 
It  may  be  said  in  general,  that  when  a  solution  is  not  perfectly 
clear  and  transparent,  it  contains  a  precipitate,  it  will  readily 
be  appreciated  that  the  degree  of  dilution  of  a  solution  has  a 
great  deal  to  do  with  the  appearance  of  any  precipitate  which 
may  be  formed.  In  most  cases  it  is  possible  to  dilute  the  solu- 
tion with  ;o  much  water  that  the  precipitate  will  be  invisible 
or  will  ncc  be  formed  at  all.  It  is  advisable,  in  order  to 
become  acquainted  with  each  precipitate  under  varying  condi- 
tions, for  the  student  to  execute  "ach  precipitative  reaction  in 
a  highly  dilute  and  also  in  a  more  concentrated  solution. 

FILTRATION. 

18.  For  the  purpose  of  separating  a  solution  from  the  pre- 
cipitate formed  in  it,  the  operation  of  filtration  is  resorted  to. 
A  filter  paper  should  be  carefully  folded,  pressed  in  the  fun- 
nel, and  moistened,  so  as  to  adhere  so  closely  to  the  funnel  as 
to  admit  no  air  down  the  sides.  Solutions  filter  much  more 
rapidly  when  hot  than  when  cold. 

19.  In  order  to  remove  the  whole  of  the  solution  adhering 
to  a  precipitate,  the  latter  is  to  be  washed,  by  directing  a 
stream  from  the  wash-bottle  around  the  upper  edge  of  the 
filter,  until  it  is  full.  When  this  water  has  all  run  through,  the 
operation  is  to  be  repeated  as  often  as  may  be  necessary.  In 
order  to  determine  when  the  operation  is  completed,  catch  a 
few  drops  of  the  filtrate  upon  a  perfectly  clean  piece  of  plati- 
num foil  and  evaporate  cautiously  over  a  small  Bunsen  flame. 
If  no  residue  is  left  upon  the  foil,  the  washing  is  complete, 


w 


iij 


iJH«C-,j,v*w'*;/-*AiKi**»*Swa#*<Wi'»*»<^^ 


'i<<M*«U»a 


T 


ONS. 


f§'9 


§»] 


TEST  PAPERS. 


n   the   temperature, 
at  higher  than  at 

gether  and  produce, 
»und,  the  latter  will 
is,  if  abundant,  will 
1,  leaving  the  latter 
quantity  or  in  a  very 
nded  for  a  long  time 
r  as  an  opalescence, 
ution  IS  not  perfectly 
tate.  It  will  readily 
n  of  a  solution  has  a 
ny  precipitate  which 
ale  to  dilute  the  solu- 
itate  will  be  invisible 
ivisable,  in  order  to 
under  varying  condi- 
jcipitative  reaction  in 
trated  solution. 


iolution  from  the  pre- 
tration  is  resorted  to. 
I,  pressed  in  the  fun- 
osely  to  the  funnel  as 
ons  filter  much  more 

the  solution  adhering 
ished,  by  directing  a 
le  upper  edge  of  the 
ts  all  run  through,  the 
nay  be  necessary.     In 

is  completed,  catch  a 
y  clean  piece  of  plati- 
a  small  Bunsen  flame. 

washing  is  complete, 


otherwise  not.  Sometimes  other  methods  are  employed  for 
ascertaining  when  the  washing  is  finished.  These  will  be  speci- 
fied in  their  proper  connection.  Never  omit  to  assure  your- 
self that  the  washing  is  thoroughly  done. 

EVAPORATION  AND  CRYSTALLIZATION. 

20.  When  water  is  removed  from  a  solution,  the  limit  of 
solubility  of  the  substance  dissolved  will  be  reached.     At  this 
point  the  latter  will  separate,  very  often  in  ti.w  form  of  crystals. 
The  most  common  way  of  removing  the  water  is  by  means  of 
evaporation.     Evaporation  may  be  effected:  first,  by  simply  CrysulH- 
exposing  the  solution  to  the  air  at  ordinary  temperatures,  in  »«<>"  by 
which  case  the  evaporation  is  called  spontaneous;  second,  by  "''"P*"'*' 
warming  the  solution  in  an  open  vessel  on  a  sand  or  water 

bath;  third,  by  direct  boiling.  The  formation  of  crystals  is  an 
operation  that  demands  time,  and  we  accordingly  find  that 
slow  evaporation  produces  larger  and  more  perfect  crystals, 
than  rapid. 

If  water  \i  saturated  with  a  crystalline  solid  (copper  sul- 
phate for  example),  at  a  high  temperature  and  then  cooled,  a  Crystaiil- 
portion  of  the  substance  will  usually  crystallize  out,  the  amount  «*"<"*  ^y 
depending  on  the  difference  in  solubility  of  the  body  at  the 
two  temperatures. 

Crystallization  is  to  be  regarded  as  a  particular  case  or  form 
of  precipitation.  It  is  the  process  most  often  resorted  to  for 
the  purification  of  many  chemical  reagents. 

USE  OF  TEST  PAPERS. 

21.  Two  kinds  of  test  paper,  litmus  and  turmeric,  are 
chiefly  employed  for  ascertaining  the  reaction  of  a  solution.  Litmus 
Litmus  paper  is  turned  red  by  substances  which  have  an  acid  P»P«''- 
reaction.     Among  these  are  most  free  acids,  many  normal  Acid  reac- 
salts,  such  as  aluminium  sulphate,  copper  sulphate,  etc.,  etc.,  '*°"' 
and  many  acid  salts  such  as  KHSO4. 

22.  Reddened  litmus  paper  is  turned  blue  by  substances 
which  have  an  alkaline  reaction,  such  as  ammonia,  and  the  reaction, 
hydrates  of  sodium,  potassium,  calcium,  barium,  strontium, 


n 


i' 


!   i 


SO 


METHODS  AND  MANIPULATIONS. 


[•>4 


hj'drate* 
and  car- 
bonate)). 


magnesium  and  lead,  and  by  the  carbonates  of   ammonium, 
sodium,  potassium  and  calcium.  Kr«„„:.h 

The  yellow  color  of  turmeric  paper  .s  turned  to  brownish 
Reaction  oi^^^    bv    substances    having    an   alkaline   reaction,   such   as 
ammonia,  and  the   hydrates   of  sodium.  P^^^^^"^'  ^^j^^l^' 
barium  and  strontium,  and  by  the  normal  carbonates  of  sodium, 
Na,COH,  and  potassium,  KjCOh. 

2-1      Sodium  bicarbonate,  NaHCO»,  and  potassmm  bicar- 

Reaction  feonate,  KHCOb,  give  no  alkaline  reaction  with  turmeric  paper 

°1^««=-    when  pure,  but  do  so  with  reddened  litmus.     By  this  me^» 

'^""'""    we  may  detect  very  small  quantities  of  Na,CO,  or  K,v.O„ 

when  mixed  with  NaHCO„,  or  KHCOg. 

24.  Other  colored  test  papers  besides  these  are  sometimes 
employed  for  detecting  the  acidity  or  alkalinity  of  so"^--^ 
The  most  important  of  these  is  lacmoid  paper.     This  closely 

resembles  litmus,  it  being  turned  -^  ^^ ^f  ^t W  i  b  n^^ 
alkalies.  It  differs  from  litmus  paper  m  the  fact  that  it  is  not 
reddened  by  the  normal  salts  referred  to  m  §21.       ^ 


» Among  these  may  be  mentioned— 
Congo  paper,  blue  with  acids,  red  with  alkalies 
Haematoxylln,  yellow  with  acids,  violet  with  alkalies. 
Aurin,  yellow  with  acids,  red  with  alkalies. 


^smm'smm?m7^^s^^ssm^'^-- 


i  .  ■ 


T 


*^ 


[§>4 

18  of   ammonium, 

irned  to  brownish 
reaction,  such  as 
)ta8sium,  calcium, 
jonntes  of  sodium, 

1  potassium  bicar- 
ith  turmeric  paper 
I.  By  this  means 
faaCOg  or  KafJO,, 

lese  are  sometimes 
inity  of  solutions.! 
per.  This  closely 
acids  and  blue  by 
e  fact  that  it  is  not 

^21. 


CHAPTER  II, 


REACTIONS  OF  THE  BASES. 


SYNOPSIS  OF  THE  CLASSIFICATION  OF  THE  BASES. 
25.     The  more  commonly  occurring   bases   are  divided 

into  six  groups,  according  to  the  behavior  of  their  solutions  to  ^'o"? 

..  ii't  ii-*j     reagent*, 

the  group-reagents,  hydrogen  sulphide,  ammonmm  sulphide 

and  ammonium  carbonate. 

Tin,  Precipitated  as   sulphides 

Antimony,  by  hydrogen  sulphide,  from 

GROUP  VI.     Arsenic,  acidified  solutions.   The  pre- 

GoLD,  cipitate  is  soluble  in   yellow 

Platinum.  ammonium  sulphide. 


GROUP  V. 


Silver, 

Mercury, 

Bismuth, 

Lead, 

Copper, 

Cadmium. 


Precipitated  as   sulphides 
iom  acidified  solutions.  The 
precipitate  is  insoluble  in  yel- 
low ammonium  sulphide. 


Cobalt, 
Nickel,    , ,. 
GROUP  IV.     Iron, 

Manganese, 
Zinc. 


Precipitated  from  neutral 
or  alkaline  solutions  by  hy- 
drogen sulphide  or  ammo- 
nium sulphide,  as  sulphides. 
Not  precipitated  by  hydrogen 
sulphide  from  acidified  solu- 
tions. 


It 


^ 


r,   .  T-  fi. 


■T 


ii 


f«' 


! 


1 
1  i' 


13 


RR ACTIONS  OF  THE  BASES. 


f§j8 


GROUP  III. 


NaOH. 


Aluminium, 

Chromium, 

(Berylmum). 


Not  precipitated  a«  sul- 
phides, from  cither  acid  or 
neutral  solutions,  by  hydro- 
gen sulphide  or  ammonium 
sulphide.  F'recipitated  as 
hydrates  by  ammonia  or  am- 
monium sulphide. 


GROUP  II. 


Barium, 
Calcium 
Strontiuv 

(Magnesiuv). 


Not  precipitated  by  hydro- 
gen sulphide,  ammonium  sul- 
phide or  ammonia.  Precip- 
itated as  carbonates  from 
neutral  solutions  by  ammo- 
nium carbonate. 


GROUP  I. 


Potassium, 

Sodium, 

Ammonium. 


Not  precipitated  by  either 
o'  the  foregoing  group-re- 
ag  ^nts. 


GPOUP  I. 
SODIUM,  POTASSIUM,  AdMONIUM.  ' 

26.  The  bases  of  the  first  group  ;.re  distinguished  by  the 
almost  universal  solubility  of  their  c  impounds.  Their  hy- 
drates, carbonates  and  sulphides  are  sc  'uble  in  water,  to  which 
they  impart  an  alkalin'^  reaction. 

SODIUM,  Ka  '  ^ 

27.  Metallic  sodium  exhibits  en  a  fresh  cut  surface  a 
metallic  lustre,  which  quickly  tarnis'ies  when  exposed  to  moist 
air.  It  reacts  vehemently  with  'vater,  liberating  hydrogen 
and  forming  sodium  hydrate,  a  caustic  deliquescent  solid, 
which  exhibits  an  alkaline  reaction  even  in  highly  dilute 
solutions. 

28.  Sodium  compounds  a  "e  somewhat  volatile  at  the 
temperature  of  the  Bunsen  flame,  to  which  they  impart  an 


e? 

cc 

P^ 
c\ 

inl 


u 


■A..  .  ■r'i.«Voi'l'-Jit«*A  **(iTS««fc-«**a»Miiii»,-i.iVft.i,;.v,vu;*'.«;*Ji^^  <aifeT3S«'*aS5SJj^''^«'Wr 


T 


cipitated  as  sul- 
r\  either  acid  or 
utions,  by  hydro- 
de  or  ammonium 
Precipitated  as 
y  ammonia  or  am- 
ilphide. 

;ipitated  by  hydro- 
iti,  ammonium  sul- 
mmonia.  Precip- 
carbonates  from 
lutions  by  ammo- 
ion  ate. 

;cipitated  by  either 
regoing  group-re- 


§331 


BASES  OF  THB  F/PST  GROUP. 


S3 


NIUM. 


listinguished  by  the 
ounds.  Their  hy- 
;  in  water,  to  which 


resh  cut  surface  a 
en  exposed  to  moist 
liberating  hydrogen 
deliquescent  solid, 
;n   in   highly   dilute 

hat  volatile    at  the 
lich  they  impart  an 


intense  yellow  color  (*^7).     This  is  an  extraordinarily  sensi- 
tive reaction,  by  means  of  which  sodium  may  be  detected  in 

.  .  Ill  ^  •     H«me 

dust,  perspiration  and  most  natural  products.     Its  great  sensi-  ^^^^.^^g„  ^i 
tiveness  makeR  it  necessary  to  observe  special  caution  in  the  •odium, 
application  of  this  test,  since  sodium,  when  present   only  in 
minute  traces  as  an  accidental  impurity,  may,  otherwise,  be       , 
taken  for  an  essential  constituent. 

ag.     Some   silicates  containing  sodium   are  volatile  with  Detection 
difficulty,  and    exhibit    the   reaction    well,  only   when    finely  of  Na  In 
pulverized  and  moistened  with  sulphuric  acid  before  being  ••"catci. 
introduced  into  the  flame. 

30.  Sodium  chloride,  when  treated  with  platinum  chlor- 
ide, forms  sodium  chloro-platinate,  NajPtCU,  a  soluble  salt.  Ruction 
which  on  cautious  evaporation  of  the  solution  appears  as  long,  with 
prismatic,   yellow   crystals,   easily   distinguishable    from   the  P'<^'«- 
corresponding  potassium  and  ammonium  salts.     (See  below.) 

POTASSIUM,  K' 

31.  Potassium  oxidizes  readily  when  exposed  to  moist  air  MeulHc 
or  oxygen.     When  thrown  on  water  it  liberates  hydrogen,  potatilum. 
which   burns   with   u   characteristic   violet   flame,  potassium 
hydrate  being  formed. 

K  -+-  H,0  =  KOH  +  H 
Potassium  hydrate  is  a  very  soluble,  deliquescent,  caustic 
solid  with  a  strong  alkaline  reaction.     It  decomposes  the  salts 
of  most  metals,  forming  hydrates,  which  in  some  cases  are 
soluble  in  an  excess. 

Most  potassium  compounds  are  volatile  at  the  temper- 


KOH. 


32 


Flame 
test 


ature  of  the  Bunsen  flame,  to  which  they  impart  a  violet  color. 
Nearly  all  the  salts  of  this  metal  are  readily  soluble  in  water,  ^r  k. 
exceptions  being  the  acid  potassium  tartrate,  KHC4H4O6,  and 
potassium  chloro-platinate,  K2PtCl6. 

33.     If  a  potassium  salt,  (especially  KCl),  in  moderately 
concentrated  solution,  be  treated  with  hydrochloric  acid  and  ^J^^^P^^- 

,.  ,  .    .  ,  .         tlon  of 

platinum  chloride,  a  crystalline,  yellow  precipitate  of  potassium  KjPtCi,. 
chloro-platinate,  K2PtCl6,  appears  either  at  once  or  after  stand- 
ing some  time.     Under  the  microscope  this  precipitate  is  seen 


'4:i 


4* 


it. 

A.' 


«-^ 


^ 


i 


Hi 


^s.-mg^'^ms^simim^- 


m 


M^ 


ri'f'i . 


I: 


14 


REACTIONS  OF  THE  BASES. 


»37 


"Cream  of 
Tartar." 


to  consist  of  octahedral  crystals.  It  is  somewhat  soluble  in 
water  and  the  addition  of  an  equal  bulk  of  alcohol  to  the 
solution  makes  the  reaction  more  delicate,  Salts  of  all  other 
bases,  excepting  sodium  and  magnesium,  should  be  absent 
when  this  test  is  applied. 

34.  If  sodium  tartrate  or  free  tartaric  acid  be  added  to  a 
moderately  concentrated  neutral  solution  of  a  potassium  salt 

KHCiH^O,,  and  the  mixture  then  strongly  acidified  with  acetic  acid,  a 
crystalline  precipitate  of  acid  potassium  tartrate,  KHC4H4O6 
will  form  on  standing. 

Violent  agitation  facilitates  the  formation  of  this  precipitate 
and  the  addition  of  alcohol,  in  bulk  equal  to  the  solution, 
makes  the  test  more  delicate.  Sodium  salts  give  no  precipitate 
with  tartaric  acid. 

35.  The  violet  color  which  potassium  compounds  impart 

Detection  the  Bunsen  flame  is  usually  used  as  a  test,  which  is,  however, 

o  potassi-  ^^^  ^^       delicate  although  characteristic.    All  other  substances 

um  by  •'  ° 

flame  test  which  color  the  flame  must  be  absent.     Magnesium  and  am- 

In  pres-  monium  compounds  do  not  interfere.  If  sodium  is  present,  the 
flame  must  be  observed  through  one,  two  or  three  thicknesses 
of  cobalt  glass.  This  blue  glass,  if  used  in  sufficient  thickness, 
completely  shuts  off  the  yellow  sodium  light  but  allows  the  pot- 
assium flame  to  shine  through,  with  a  somewhat  reddish  tinge. 


ence  of 
sodium. 


.,        1                       Salts  of 

1'  ^ 

'  ;  ,                           Decompo- 
j  1                             sition  of 
!                                NH3  com- 
pounds by 
heat. 

!. 

',  1 

AMMONIUM,  (NHi)'- 

36.  Ammonia  (NH3)  is  a  pungent  gas,  highly  soluble  in 
water,  to  which  it  imparts  its  characteristic  odor  and  basic 
properties. 

It  combines  with  acids  directly  to  form  salts  t)f  the  hypo- 
thetical radical  ammonium,  (NH4),  for  example 

2NH8    -I-    H2SO4    =     (NH4)2S04 

Ammonium  salts  are  odorless,  ammonium  carbonate  being 
an  exception,  and  usually  soluble  in  water. 

37.  Ammonium  salts  are  decomposed  and  volatilized  at 
a  temperature  below  redness.  They  may  be  oxidized  and 
removed  from  a  concentrated  solutio.n  by  continued  boiling 
with  an  excess  of  concentrated  nitric  acid,  followed  by  evapo- 


iiJ  i 


ift.,).^!.^,.       .*s,;,i-..,*Xi*fsv,^i!fetfe:; 


."•SfaiMa»^,-.. 


*h. 


vNf 


T 


mi 

omewhat  soluble  in 
:  of  alcohol  to  the 
,  Salts  of  all  other 
I,  should  be  absent 

;  acid  be  added  to  a 
of  a  potassium  salt 
with  acetic  acid)  a 

tartrate,  KHC4H4O6 

,n  of  this  precipitate 
jual  to  the  solution, 
ts  give  no  precipitate 

■n  compounds  impart 
It,  which  is,  however. 
All  other  substances 
Magnesium  and  am- 
sodium  is  present,  the 
o  or  three  thicknesses 
in  sufficient  thickness, 
Tht  but  allows  the  pot- 
mewhat  reddish  tinge. 


gas,  highly  soluble  in 
eristic  odor  and  basic 

,rm  salts -of  the  hypo- 
example 

H4)2S04 

anium  carbonate  being 

ter. 

osed  and  volatilized  at 

r  may  be  oxidized  and 

1   by  continued  boiling 

cid,  followed  by  evapo- 


§42] 


BASES  OF  THE  SECQND  GROUP. 


IS 


ration  to  dryness.    They  should  be  removed  before  applying 
the  tests  for  potassium  mentioned  in  §§33  or  34. 

38.  If  an  ammonium  salt  be  rendered  alkaline  with  sodium 
or  potassium  hydrate  and  warmed,  ammonia  will  be  set  free 
and  may  be  perceived  by  its  characteristic  odor  and  alkaline 
reaction.  To  observe  the  latter,  cut  a  slit  in  a  cork  fitting  the 
test  tube  which  contains  the  ammonium  salt  and  potassium 
hydrate.  Suspend  a  narrow  strip  of  red  litmus  paper  from 
the  slit  of  the  cork,  and  set  the  latter  loosely  in  the  test  tube, 
in  such  a  way  that  it  will  hang  freely  without  touching  the 
sides,  or  the  liquid.     If  it  turns  blue,  ammonia  is  present. 

NH4CI  +  KOH  =  KCl  +  NHg  +  H3O 

39.  Ammonium  chloride  gives,  with  hydrochloric  acid  and 
platinum  chloride,  a  reaction  similar  to  that  of  the  potassium 
salts;  the  precipitate  being,  in  this  case,  ammonium  chloro- 
platinate,  (NH4)2PtCl6,  indistinguishable  from  potassium 
chloro-platinate  (§33)- 

40.  Nessler's  reagent,  a  soluHon  of  mercuric  iodide  with 
an  excess  of  potassium  hydrate  (see  table  of  reagents), 
produces  in  very  dilute  solutions  of  ammonia  or  ammonium 
salts,  a  reddish  brov^rn  coloration  or  precipitate.  This  reaction 
is  adapted  to  the  detection  of  minute  traces  of  ammonia,  such, 
for  example,  as  those  which  are  often  found  in  contaminated 
drinking  water.     (See  Special  Part,  §332)- 

GROUP  II. 
CALCIUM,  BARIUM,  STRONTIUM,  (MAGNESIUM). 

41.  The  bases  of  the  second  group  are  distinguished  from 
those  of  the  first,  by  the  fact  that  their  normal  carbonates 
and  phosphates  are  insoluble  in  water.  They  are  distinguished 
from  those  of  groups  III,  IV,  V,  and  VI  by  the  fact  that  dilute 
solutions  of  their  salts  are  not  precipitated  either  by  ammonia, 
ammonium  sulphide  or  hydrogen  sulphide. 

42.  Ammonium  carbonate,  when  added  to  a  neutral  solu- 
tion, will  precipitate  all  the  bases  of  this  group  as  carbonates. 
The  precipitation  of  magnesium  carbonate  is  incomplete  and 


Decompo- 
sition by 
alkalies. 


Ammoni- 
um chloro- 
platinate. 


Ciiaracter- 
istics  of 
salts  of 
Ca,  Ba,  Sr 
and  Mg. 


Precipita- 
tion of 
CaCOj, 
BaCOa, 
and  SrCOt 


m 


Nessler's 
test  for 

K 

NH,. 

i- 

"J 

if 


■*«iwan^^^« 


i6 


REACTIONS  OF  THE  BASES. 


[848 


Ca, 

flame 

reaction. 


CaS04+ 
3H1O. 


Ca  precip- 
itated b}- 
sodium 
phospate. 


Oxalate 
test  for  Ca. 


Sr, 

flame 

reaction. 


Strontium 
sulpliate. 


may  be  entirely  prevented  by  the  addition  of  a  sufficient 
quantity  of  ammonium  chloride.  The  precipitated  carbonates 
may  be  pasty  at  first,  but  by  gently  warming  the  solution  in 
which  they  are  formed,  they  gradually  become  granular.  In 
this  condition,  they  subside  and  filter  more  readily. 

CALCIUM,  Ca"- 

43.  Calcium  compounds,  especially  the  salts  of  calcium 
with  the  haloid  acids,  CaCl2  etc.,  impart  an  orange  or 
orange-red  color  to  the  Bunsen  flame. 

44.  Solutions  of  calcium  salts  give,  with  sulphuric  acid  or 
a  soluble  sulphate,  a  crystalline  precipitate  of  calcium  sulphate, 
CaS04,2H20,  (gypsum).  Since  this  precipitate  is  somewhat 
soluble  in  water,  it  will  only  appear  in  moderately  concen- 
trated solutions. 

45.  Sodium  phosphate,  NaaHPOi,  when  dded  to  an  alka- 
line solution  of  a  calcium  salt,  produces  a  flocculent  precipitate 
of  tri-calcium  phosphate,  Ca3(P04)2,  soluble  in  acids,  even  in 
dilute  acetic. 

46.  Neutral  or  alkaline  solutions  of  calcium  salts  give, 
with  ammonium  oxalate,  even  in  highly  dilute  solutions,  a 
micro-crystalline  precipitate  of  calcium  oxalate,  CaCa04-|-2HjO 
insoluble  in  dilute  acetic  acid  or  in  ammonia,  soluble  in  the 
mineral  acids. 

STRONTIUM,  Sr  «•  -  " 

47.  Strontium  compounds,  especially  salts  of  the  haloid 
acids,  (SrCl2  etc.),  impart  an  intense  crimson  color  to  the 
dame. 

48.  Solutions  of  strontium  salts  give,  with  sulphuric  acid 
or  soluble  sulphates  (including  calcium  sulphate),  a  micro- 
crystalline  precipitate  of  strontium  sulphate,  SrS04.    , 

In  highly  dilute  solutions,  this  precipitate  only  appears  on 
standing  some  time.  The  reaction  with  calcium  sulphate 
solution  (which  of  course  cannot  precipitate  a  calcium  salt) 
serves  to  distinguish  solutions  of  strontium  from  those  of 
calcium  compounds. 


m\ 


.S*S«&W6^<'.!. 


.41      -BBSS«i*8F,- 


J\ 


[S48 

in  of  a  sufficient 
pitated  carbonates 
ig  the  soiutton  in 
jme  granular.  In 
eadily. 

>  salts  of   calcium 
irt    an   orange   or 

h  sulphuric  acid  or 
)f  calcium  sulphate, 
lipitate  is  somewhat 
moderately  concen- 

n  .dded  to  an  alka- 
locculent  precipitate 
ble  in  acids,  even  in 

calcium  salts  give, 
r  dilute  solutions,  a 
late,CaC204+2H,0 
Qonia,  soluble  in  the 


r  salts  of  the  haloid 
:rimson  color  to  the 

e,  with  sulphuric  acid 
sulphate),  a  micro- 
ite,  SrSOv 

itate  only  appears  on 
ith  calcium  sulphate 
)itate  a  calcium  salt) 
itium   from  those   of 


8s6] 


BASES  OF  THE  SECOND  GROUP. 


17 


49.  Sodium  phosphate  reacts  with  strontium  as  it  does  gtronUum 
wit!i  calcium  compounds  (§45).     ^^'       r   -^       *>  phosphate. 

50.  Ammonium  oxalate  reacts  with  strontium  as  it  does  strontium 
with  calcium  compounds.     The  precipitate  is  not  quite  so  oxalate, 
insoluble. 

BARIUM,  Ba"- 


Ba 
flame  test. 


BaSO*. 


51.  Barium  compounds  impart  to  the  flame  a  leaf-green 
coloration,  which  often  appears  only  after  the  platinum  wire 
has  been  held  in  the  flame  for  some  time.  Batium  sulphate 
and  the  haloid  salts  exhibit  this  reaction  well. 

52.  Sulphuric  acid  or  a  soluble  sulphate  produces,  even  in 
the  most  highly  dilute,  acid  or  alkaline  solutions  of  barium,  a 
very  finely  divided  precipitate  of  barium  sulphate,  BaSOi. 
When  calcium  sulphate  is  used  for  this  test,  the  precipitate 
appears  at  once  (distinction  from  strontium). 

53.  Sodium  phosphate  reacts  with  barium  as  it  does  with 
calcium  compounds  (§45). 

54.  Ammonium  oxalate  reacts  with  barium  as  it  does  with 
calcium  compounds.  The  precipitate,  BaCa04,  is  not  quite  so 
insoluble. 

55.  Potassium  chromate,  KjCrO*,  or  potassium  pyro- 
chromate,  KaCraO;,  produces,  in  a  neutral  solution  of  barium 
salts,  a  yellow,  finely  crystalline  precipitate  of  barium  chromate, 
BaCrO*;  insoluble  in  ammonia,  nearly  insoluble  in  dilute 
acetic  acid,  more  readily  soluble  in  dilute  mineral  acids. 
Dilute  solutions  of  strontium,  calcium  and  magnesium  salts 
give  no  precipitate  with  these  reagents. 

'  ■  MAGNESIUM,  Mg"- 

56.  Solutions  of  magnesium  salts,  when  free  from  ammo- 
nium salts,  give,  on   treatment  with   sodium,  potassium,  or 
ammonium  carbonate,  an  amorphous  precipitate  of  magnesium  ^  pQ 
carbonate,  MgCOg.     Since  this  precipitate  is  soluble  in  solu- 
tions of  ammonium  salts,  it  does  not  appear  when  the  latter 

are  present  in  sufflcient  quantity. 


Bas(P04)j. 

BaCj044- 
2HaO. 


Precipita- 
tion of 
BaCrO* 
distinguish- 
es Ba  from 
all  other 
bases  of 
Group  II. 


\ 


kit 
1 


n 


^& 


i»g!SfSiW!«»«.* 


M*iSSL. 


i8 


RB ACTIONS  OF  THE  BASES. 


[§61 


57.  If  therefore  we  add  to  a  neutral  solution  of  a  magne- 
Separatlon  sium  salt,  first,  ammonium  chloride  and,  then,  ammonium 
of  Mg  carbonate,  no  precipitate  will  appear.  This  reaction  serves  to 
Ba  Ca  Sr  <i*^^i**g'**s^  magnesium  salts  and  to  separate  them  from  those  of 

the  other  bases  of  this  group. 

58.  Magnesium  compounds  impart  no  color  to  the  flame. 

59.  The  addition  of  ammonia  to  a  solution  of  a  magnesium 
salt  precipitates  magnesium  hydrate. 

This  precipitation  is  incomplete  and  is  entirely  prevented  by 
ammonium  chloride  or  other  ammonium  salts.  A  similar  pre- 
Mg(OH)j.  cipitation  is  produced  by  the  hydrates  of  sodium,  potassium, 
barium,  or  calcium,  being  nearly  complete  in  this  case,  in  the 
absence  of  ammonium  salts  or  when  the  alkaline  solution  is 
boiled  until  all  ammonia  is  expelled.  Magnesium  hydrate  may 
be  dissolved  in  a  solution  of  ammonium  chloride. 

a.  Many  compounds  of  magnesium  (such  as  chloride, 
Blowpipe  sulphate,  carbonate,  hydrate,  nitrate),  if  strongly  ignited  and 
test  for  then  moistened  with  cobalt  nitrate  solution  and  again  ignited, 
^8-  exhibit  a  rose  or  pink  coloration. 

-,  „p.  60.     Magnesium  salts  give  no  precipitate  with  sulphuric 

is  soluble,  acid  or  with  soluble  sulphates. 

61.     If  a  magnesium  salt,  in  neutral  solution,  be  treated 
with  ammonium  chloride,  sodium  phosphate  and  with  ammo- 
nia, in  large  excess,  a  crystalline  precipitate  will  appear,  of 
110^0^  *      magnesium   ammonium   phosphate,   MgNH4P04,  soluble  in 
MgNH^POi  dilute  acids,  slightly  soluble  in  water,  insoluble  in  ammonia 
water. 

MgClj  +  NHa  +  NH4CI  +  NaaHPO*  = 
2NaCl  +  NH4CI  +  MgNH4P04  "^ 
If  the  solution  is  dilute,  this  precipitate  does  not  appear  at 
once.     Its  formation  is  aided  by  violent  shaking.     If  the  inside 
MgNH^POi  of  the  glass  tube  be  rubbed  with  a  glass  rod,  the  precipitate 
will  form  at  and  adhere  to  the  rubbed  places,  so  that  visible 
lines  may,  in  this  way,  be  drawn  upon  the  glass.     In  applying 
this  test,  the  appearance  of  a  non-crystalline  precipitate  is  not 
to  be  rega.-ded  as  indicative  of  magnesium.     Sometimes  the 
precipitate,  when  first  formed,  will  not  be  crystalline,  but  will 
become  so  on  standing  over  night  in  a  warm  place. 


must  be 
crystalline 


C| 


--*^-..»&,--ife(.'fc«a5®i;«iaK%;^* 


T 


ition  of  a  magne- 
then,  ammonium 
reaction  serves  to 
hem  from  those  of 

jlor  to  the  flame. 
)n  of  a  magnesium 

irely  prevented  by 
ts.  A  similar  pre- 
jodium,  potassium, 
in  this  case,  in  the 
alkaline  solution  is 
esium  hydrate  may 
oride. 

(such  as  chloride, 
rongly  ignited  and 
and  again  ignited, 

tate  with  sulphuric 

solution,  be  treated 
te  and  with  ammo- 
itate  will  appear,  of 
'^H4P04,  soluble  in 
isoluble  in  ammonia 

ajHP04=  " 

H4PO4" 

:e  does  not  appear  at 
laking.  If  the  inside 
i  rod,  the  precipitate 
places,  so  that  visible 
e  glass.  In  applying 
line  precipitate  is  not 
um.  Sometimes  the 
le  crystalline,  but  will 
arm  place. 


^]  BASES  OF  THE  THIRD  GROUP. 

GROUP  III. 
ALUMINIUM  AND  CHROMIUM. 

62.  The  bases  of  this  group  are  completely  precipitated 
from  their  solutions  by  ammonia,  ammonium  carbonate  or 
ammonium  sulphide,  as  hydrates.  Their  solutions  are  not 
precipitated  by  hydrogen  sulphide. 

ALUMINIUM,  Al  '"• 

63.  Aluminium  is  a  bluish  white  metal,  which  dissolves 
readily  in  hydrochloric  acid,  forming  aluminium  chloride.  It 
is  soluble  with  difficulty  in  most  oxy-acids.  Solutions  of  its 
normal  salts  have  a  strongly  acid  reaction  and  are  more  or  less 
decomposed,  on  boiling,  into  free  acid  and  basic  salt. 

64.  Ammonia  produces  in  a  solution  of  an  aluminium 
salt  a  colorless,  amorphous,  flocculent,  or  semi-gelatinous,  pre- 
cipitate of  aluminium  hydrate,  Al(OH)8,  which  is  soluble  in 
dilute  acids  and  nearly  insoluble  in  dilute  ammonia. »  This 
precipitate  is  so  transparent  that  small  quantities  of  it  may 
readily  be  overlooked.  On  standing,  it  gathers  into  larger 
flocks  and  may  then  be  more  easily  seen. 

After  washing  and  drying,  it  can  be  converted,  by  heating 
to  bright  redness  on  platinum  foil,  into  alumina,  AI2O3.  The 
latter  compound,  if  moistened  with  a  dilute  solution  of  cobalt 
nitrate  and  again  heated  in  the  oxidizing  flame,  turns  light 
blue,  a  useful  and  characteristic  reaction. 

65.  Sodium  hydrate,  when  added  to  the  solution  of  an 
aluminium  salt  causes  the  precipitation  of  aluminium  hydrate, 
which  readily  dissolves  jn  an  excess  of  the  precipitant,  forming 
the  soluble  compound,  sodium  aluminate,  Al(ONa)(OH)2. 

Potassium  hydrate  gives  a  precisely  similar  reaction. 

66.  A  solution  of  an  aluminate,  upon  exact  neutralization 
with  an  acid,  or  upon  addition  of  an  excess  of  ammonium 
chloride,  gives  a  precipitate  of  aluminium  hydrate. 

Al(ONa)(OH),  +  HCl  =  Al(OH)3  +  NaCl 
Al(ONa)(OH),  +  NH4CI  =  A1(OH)b  +  NaCl  +  NHg 


19 


Al. 


AI(OH),, 


Alumin- 
ates. 


Precipita- 
tion by 
NH«Cl  ol 
Al(OH),. 


i 


If, 


Cobalt  so- 

lution test 

1 

for  AlaO». 

>L.  Blum,  Fres.  Zeitxhrift:  27,  p.  i9- 


i^i|'7S^Rtes» 


30 


REACTIONS  OF  THE  BASES. 


t§7i 


If; 


IJ/I  i 


K  \ 


6y,     A  solution  of  an  aluminium  salt  containing  but  little 

free  acid,  if  treated  with  an  excess  of  ammonium  or  sodium 

Basic        acetate,  forms  aluminium  acetate,  which  on  boiline  is  decom- 

posed,  forming  basic  aluminium  acetate,  which  appears  as  a 

colorless,  amorphous  precipitate. 

Al(OCOCH8)8  +  HjO  =  AlO(OCOCHg)  +  2HOCOCH3 

CHROMIUM,  Crni*vi. 

68.  Chromium  is  a  brittle,  white,  extremely  hard  metal, 
easily  soluble  in  hydrochloric  acid,  with  difficulty  in   dilute 

Cr  salts,  sulphuric,  and  insoluble  in  nitric  acid.  Its  salts  are  all  colored, 
being  usually  violet  or  green,  less  often  red.  Their  solutions, 
when  boiled,  undergo  a  similar,  partial  decomposition  to  those 
of  aluminium. 

69.  Ammonia  produces,  in  solutions  o^  chromium  salts,  a 
flocculent  or  semi-gelatinous  apple-green  precipitate  of  chro- 

Cr(OH)a.  mium  hydrate,  Cr(OH)8,  which  is  insoluble  in  dilute  ammonia, 
soluble  in  acids.  When  ignited,  chromium  hydrate  loses  water, 
being  converted  into  deep  green  chromium  oxide,  CrjOg. 

70.  Sodium  hydrate  produces,  in  solutions  of  chromium 
salts,  a  precipitate  of  chromium  hydrate,  which  readily  dis- 
solves in  an  excess  of  the  precipitant,  sodium  chromite, 
Cr(OH)jONa,  being  formed.  The  latter  solution  is  decom- 
posed on  boiling,  a  sage-green  precipitate  of  hydrated  chro- 
mium oxide,  probably  CrOOH,  appearing.  Potassium  hydrate 
reacts  in  a  precisely  similar  way. 

This  re-precipitation  from  alkaline  solutions,  on  boiling, 
may  be  used  for  the  separation  of  aluminium  and  chromium, 
since  the  former  remains  in  solution,  while  ^e  latter  is 
precipitated.  '  :    . '^ 

71.  The  oxide,  hydrate,  or  salts  of  chromium,  may  be 
converted  into  chromic  acid  by  powerful  oxidizing  agents.  If 
chromium  hydrate  or  a  chromium  salt  is  warmed  with  strong 

Oxidation  nitric  acid  and  potassium  chlorate,  the  green  color  of  the 
»  "■  'mixture  will  change  to  reddish  yellow,  in  consequence  of  the 
formation  of  chromic  acid. 

2Cr(OH)8  -h  3O  =  2H2Cr04  -|-  HjO 
Cr(S04)8  +  3O  +  SHaO  =  aHjCrO,  +  sHjSO* 


Alkaline 
Cr  solu- 
tions. 


iv&;#;»'*v'.>,w^,=;N«aj^!S>**«^6»i>i 


.Mm^^s^i^^,-'' 


■.,tM\'-'yrf-:^tm 


T 


mtaining  but  little 

ionium  or  sodium 

boiling  if  decom- 

hich  appears  as  a 

,)  +  2HOCOCH3 


emely  hard  metal, 
difficulty  in  dilute 
ilts  are  all  colored, 
.  Their  solutions, 
Dmposition  to  those 

f  chromium  salts,  a 
precipitate  of  chro- 
!  in  dilute  ammonia, 
lydrate  loses  water, 
I  oxide,  CrjOg. 
itions  of  chromium 
which  readily  dis- 
sodium    chromite, 
r  solution  is  decom- 
e  of  hydrated  chro- 
Potassium  hydrate 

>lutions,  on  boiling, 
ium  and  chromium, 
while  the   latter   is 

chromium,  may  be 

oxidizing  agents.     If 

warmed  with  strong 

green  color  of  the 

consequence  of  the 

),  +  H,o      ; 


S7S] 


BASES  OF  THE  FOURTH  GROUP. 


21 


Similarly,  a  chromium  salt  or  Cr(OH)«,  may  be  converted 
into  a  chromate  by  fusion  with  potassium  nitrate  and  sodium 
carbonate. 

Cra(S04)«  +  sNajCOa  +  3KN0g  = 
SNaaSO*   +  2NaaCr04  -f  3KNO,  -f-  sCOj 

a.    To  effect  this  change,  mix   the  chromium   compound 

with  about  ten  purts  of  sodium  carbonate  and  one  part  of 

potassium  nitrate.    Fuse  the  mass  for  five  minutes  on  platinum 

foil.     Dissolve  the  product  in  water.     Its  intense  yellow  color 

shows  the  presence  of  a  chromate,  and  therefore  of  a  chro-  Confirma- 

mium   compound    in   the  original    substance.      Acidify  this  tory  test 

solution  with  acetic  acid  and  then  add  lead  nitrate,  when  a  *"!,'",.„.. 

compounds. 

yellow  precipitate  of  lead  chromate  will  be  formed  (r.  §221). 
This  confirmatory  test  should  never  be  omitted,  since  the 
yellow  color  of  chromic  acid  and  of  chromates  is  much  more 
intense  and  more  characteristic  than  the  green  color  of  the 
chromium  salts. 

72.  Chromium   compounds   give   a  green   color  to  the 

borax  bead  in  oxidizing  and  reduction  flames  (§7)*  borax  bead. 

73.  A  solution  of  a  chromium  salt  containing  but  little 
free  acid,  if  t'*eated  with  an  excess  of  ammonium  or  sodium 
acetate,  forms  chromium  acetate,  which,  on  boiling,  is  decom- 
posed, forming  basic  chromium  acetate,  which  appears  as  an  ^"*'*= 
apple-green,  amorphous  precipitate. 

Cr(OCOCH8)8-|-H20  =  CrO(OCOCH8)+2HOCOCH8 

GROUP  IV. 
COBALT,  NICKEL,  IRON,  MANGANESE  AND  ZINC. 

74.  Bases  of  this  group  give,  with  ammonium  sulphide 
in  neutral  or  alkaline  solutions,  a  precipitate  of  the  corres- 
ponding sulphides.  In  acid  solutions  they  give  no  precipitate 
with  hydrogen  sulphide.  They  are  precipitated  by  sodium 
carbonate  as  carbonates  or  basic  carbonates. 

.,    :       u     ,  .  ■         COBALT,  Con»in. 

75.  Cobalt  is  a  white,  magnetic  metal,  which  dissolves  ^^^^^ 
readily  in  dilute  acids  to  form  cobaltous  salts,  the  solutions  of 
which  are  red,  although  the  anhydrous  salts  are  blue  or  violet. 


% 


1} 
%. 


% 


Ju 


,i^i,i|<srTi3^»)^®'"«»* 


32 


REACTIONS  OF  THE  BASES. 


[«8^ 


^;;f 


Cos. 


Co(OH)a. 


Borax 
bead  reac- 
tion. 


Reduction 
on  char- 
coal of  Co. 


Reaction 

with 

KNO,. 


76.  Neutral  solutions  of  cobaltous  salts  give,  with  ammo- 
nium sulphide,  a  black  precipitate  of  cobaltous  sulphide,  CoS» 
insoluble  in  cold,  dilute  hydrochloric  acid. 

77.  Ammonia  produces  in  cobaltous  solutions  a  blue  pre- 
cipitate of  cobaltous  hydrate,  soluble  in  an  excess  of  ammonia. 
Ammonium  salts  prevent  the  formation  of  this  precipitate. 

78.  Bora.\  dissolves  cobalt  compounds,  in  either  oxidizing 
or  reducing  flame,  to  a  deep  blue  bead  (§9)< 

79.  Cobalt  compounds,  when  heated  on  charcoal  with 
sodium  carbonate,  in  the  reducing  flame,  are  reduced  to 
metallic  cobalt,  which  appears  in  the  form  of  magnetic  particles 
when  the  fused  mass  ia  treated  with  water  (^12). 

80.  When  a  cobalt  solution  is  mixed  with  potassium  nitrite 
in  excess  and  then  strongly  acidifled  with  acetic  acid,  the  cobalt 
separates,  after  standing  for  some  time  in  a  warm  place,  as  a 
canary-yellow,  crystalline  precipitate  of  tri-potassium  cobaltic 
nitrite,  K3Co(N02)8.  ,; 


I't. 


ml 


Salts  of 
Ni. 


Precau- 
tions in 
the  precip 
itation  of 

NiS. 


Ni(OH),. 


Borax 

bead 

reaction. 


NICKEL,  Ni  "*•"• 

81.  Nickel  is  a  silvery  white,  magnetic  metal,  which  dis- 
solves readily  in  warm  dilute  acids,  forming  green  nickelous 
salts,  which  are  usually  yellow  when  anhydrous. 

8a.  The  addition  of  ammonium  sulphide,  to  a  neutral  or 
an  alkaline  solution  of  nickel  salts,  produces  a  black  precipita  «; 
of  nickel  sulphide,  NiS,  insoluble  in  cold,  dilute  hydrochloric 
acid.  This  precipitate  is  somewhat  soluble  in  an  excess  of 
ammonium  sulphide  and  ammonia,  the  solution  having  a 
brownish  color.  An  excess  of  the  precipitant  should  be 
avoided.  The  addition  of  ammonium  chloride  aids  the  com- 
plete precipitation. 

83.  Ammonia  produces,  in  solutions  of  nickel  salts,  a  green 
precipitate,  which  dissolves  very  readily  in  an  excess  of  ammo- 
nia, giving  a  deep  blue  ..v^iution. 

84.  Borax  dissolves  nickel  compounds  in  the  oxidizing 
flame  to  a  clear  brown  bead  (violet  while  hot),  which,  in  the 
reducing  flame,  becomes  gray  and  then  colorless. 


»^(*ii^tel|KS*i»iviia6S'J*v 


«.» 


give,  with  atnmo- 
3US  sulphide,  CoS, 

lutions  a  blue  pre- 
ixcess  of  ammonia, 
his  precipitate, 
in  either  oxidizing 

)• 
on  charcoal  with 

;,  are  reduced  to 
[  magnetic  particles 
(§12).  ■  ;  f   • 

lb  potassium  nitrite 
i:etic  acid,  the  cobalt 
a  warm  place,  as  a 
i-potassium  cobaltic 


:ic  metal,  which  dis- 
ing  green  nickelous 
drous. 

lide,  to  a  neutral  or 
s  a  black  precipita  «? 
,  dilute  hydrochloric 
uble  in  an  excess  of 
1  solution  having  a 
recipitaot  should  be 
loride  aids  the  com- 

)f  nickel  salts,  a  green 
1  an  excess  of  ammo- 

nds  in  the  oxidizing 
le  hot),  which,  in  the 
colorless. 


[«9) 


BASES  OF  THE  FOURTH  GROUP. 


n 


85.    Nickel  compounds,  when  heated  on  charcoal   with 


sodium  carbonate  in  the  reducing  flame,  are  reduced  to  metal-  J^^^J^ 
lie  nickel,  which  appears  in  the  form  of  magnetic  spangles  co,i  of  Ni. 
when  the  fused  mass  is  treated  with  water. 

86.     Nickelous  salts,  when  treated  with  potassium  nitrite  ^/jY'rom 
and  acetic  acid,  as  in  §80,  are  not  precipitated. 


Co. 


IRON,  Fe«»"'- 


reaction. 


87.  Iron  dissolves  in  dilute  acids,  forming  ferrous  salts, 
which  are  usually  colorless  or  pale  green.     They  may  be  con-  Salts  o£ 
verted  into  ferric  salts  by  treatment  with  boiling  nUric  acid,  |^^e^" 
chlorine,  bromine,  or  other  oxidizing  agents.  p^  ui. 

Ferric  solutions  may  readily  be  reduced  to  ferrous  by  treat- 
ment with  hydrogen  sulphide  or  other  reducing  agents. 
2FeCl8  +  HjS  =  aPeCla  +  2HCI 

88.  Borax  dissolves  iron  compounds,  in  the  oxidizing  Borax 
flame,  to  a  clear  bead,  which  is  red  while  hot,  yellow  when  bead^ 
cold.     In  the  reducing  flame  the  bead  turns  bottle-green. 

89.  Iron   compounds,   when   heated    on    charcoal    with  Reduction 
sodium   carbonate   in   the   reducing   flame,   are   reduced    to  of  Fe  on 
metallic  iron,  which  appears  in  the  form  of  magnetic  particles  charcoal, 
when  the  fused  mass  is  treated  with  water. 

90.  Solutions  of  ferrous  or  ferric  salts  give  with  ammo- 
nium sulphide  a  black  precipitate  of  ferrous  sulphide,  FeS,  ^^^ 
readily  soluble  in  cold,  dilute  hydrochloric  acid.  This  precipi- 
tate, when  exposed  to  the  air  in  a  moist  condition,  readily 
oxidizes  to  ferrous  sulphate,  etc.  It  should,  therefore,  be 
filtered  and  washed  as  rapidly  as  possible. 


Ferrous  Salts. 


Fe  n  salU. 


91.     Ammonia  produces,  in  solutions  of  ferrous  salts,  a 
colorless  precipitate  of  ferrous  hydrate,  which,  by  oxidation,  Fe(OH),. 
very  rapidly  turns  green,  then  black,  finally  reddish  brown. 
The  hydrates  of  sodium  and  potassium  give  a  similar  reaction. 

ga.  A  neutral  or  acid  solution  of  a  ferrous  salt  gives,  with  Fe5(CN)u, 
potassium  ferricyanide,  a  deep  blue  precipitate  of  TurnbulVs  TumbuU's 
blue,  the  composition  of  which  is  variable.  *''"*'" 


;  t 


w^ 


^^^mmmum 


mmmmrnn^^^-'  • 


■'^^' 


H 


REACT/OJVS  OF  THE  BASES. 


t§9» 


t  r 


Fein 
mIU. 


Fe(OH),. 


Ferric  ii 
ricyanlde 
as  a  test 
forSOa, 
etc. 


Prussian 
blue. 


Sulpho- 
cyanate 
test  for 
rem. 


93.  A  neutral  or  atid  solution  of  a  ferrous  salt  gives,  with 
potassium  ferrocyanide,  a  pale  blue  precipitate,  which  rapidly 
turns  deep  blue. 

94'  A"  acidified  solution  of  a  ferrous  salt  is  not  alt«?red 
by  potassium  sulphocyanate. 

Ferric  Salts. 

95'  Solutions  of  normal  ferric  salts  are  usually  yellow  or 
red  and  have  a  distinctly  acid  reaction  towards  litmus  paper. 

Ammonia  produces  an  amorphous,  reddish  brown  precipi- 
tate of  ferric  hydrate,  Fe(OH)„  entirely  insoluble  in  an  excess 
of  the  precipitant. 

FeCl»  +  3H3O  -f-  3NHh  =  Fe(OH)«  +  3NH4CI 

The  hydrates  of  sodium  or  potassium  give  an  exactly  simi- 
lar reaction. 

Ferric  hydrate  is  readily  soluble  in  alkaline  solutions  which 
contain  glycerine,  sugar  or  tartaric  acid;  many  other  kinds  of 
organic  substances  producing  a  similar  effect. 

96.  A  neutral  or  acid  solution  of  a  ferric  salt  gives,  with 
potassium  ferricyanide,  a  reddish  brown  coloration,  but  no 
precipitate. 

This  mixture  is  turned  blue  by  many  reducing  agents,  such 
as  hydrogen  sulphide,  sulphurous  acid,  stannous  chloride, 
metallic  zinc,  etc.,  and  is  often  employed  as  a  reagent  to  test 
for  reducing  agents.  Paper  dipped  in  this  solution  can  be 
preserved  in  the  dark  and  used  as  a  test  paper  for  reducing 
substances.  It  is  called  "  blue  paper "  because  it  is  turned 
blue  by  the  light  or  by  the  compounds  named. 

97.  A  neutral  or  acid  solution  of  a  ferric  saU  gives,  with 
potassium  ferrocyanide,  a  blue  coloration  or  a  blue  precipitate, 
consisting  of  Prussian  blue.     Its  composition  is  variable. 

Prussian  blue  i3  insoluble  in  dilute  nitric,  hydrochloric  or 
sulphuric  acids,  but  dissolves  in  a  concentrated  solution  of 
oxalic  acid. 

98.  An  acid  solution  of  a  ferric  salt  is  turned  blood-red 
by  the  addition  of  potassium  sulphoc^'anate,  a  ferric  potassium 
sulphocyanate  being  formed,  of  the  composition,  Fe(SCN)8, 


tic 
hA 


^:t! 


■■^'^!l>i^>S«t^i^<iaK^i^-^ 


\ 


mmm 


J\ 


«"Hl 


BASES  OF  THE  FOURTH  GROUP. 


as 


IS  salt  gives,  with 
ite,  which  rapidly 

salt  is  not  alt'^red 


usually  yellow  or 
ards  litmus  paper, 
ish  brown  precipi- 
jluble  in  an  excess 

,+  3NH,Cl 

ve  an  exactly  simi- 

ine  solutions  which 

lany  other  kinds  of 

ct. 

ric  salt  gives,  with 

coloration,   but  no 

lucing  agents,  such 
stannous  chloride, 
IS  a  reagent  to  test 
tiis  solution  can  be 
paper  for  reducing 
ecause  it  is  turned 
tied. 

rric  salt  gives,  with 
>r  a  blue  precipitate, 
on  is  variable, 
ric,  hydrochloric  or 
jntrated  solution  of 

is  turned  blood-red 
:e,  a  ferric  potassium 
position,  Fe(SCN)8, 


9KSCN.     If   this  solution  is  shaken  with  a  little  ether,  the 
latter  will  be  colored  red. 

99.  A  solution  of  a  ferric  salt  containing  but  little  free 
acid,  if  treated  with  an  excess  of  ammonium  or  sodium  acetate, 
turns  red,  from  the  formation  of  ferric  acetate,  Fe(OCOCH8)g. 

If  this  solution  is  boiled,  all  the  iron  is  thrown  down  as  basic  aceuuc 

ferric  acetate,  a  brick-red,  flocculent  precipitate  of  variable 

composition. 

Fe(OCOCH8)8  +  HaO  =  FeO(OCOCH»)  +  aHOCOCH, 

100.  If  to  a  solution  of  a  ferric  sah,  sodium  phosphate  be 
added  in  excess,  and  then  ammonia,  a  white  precipitate  will 

be  formed,  of  ferric  phosphate,  insoluble  in  alkalies  and  acetic  ^«P0« 
acid,  soluble  in  dilute  mineral  acids. 
FeCl,  +  NaaHPO^  h  NH^  =  FePO*  -f  2NaCl  +  NH4CI 

MANGANESE,  Mnn»vii. 

101.  Manganese  is  a  brittle,  gray  metal,  which  oxidizes 
readily  in  the  air  and  dissolves  easily  in  dilute  acids,  forming 
manganous  salts,  which  are  usually  flesh  colored.  The  higher 
oxides  of  manganese,  MnjOa,  MngOi,  MnOj,  MnaOr,  etc.,  dis- 
solve in  warm  hydrochloric  acid,  forming  manganous  chloride 
and  free  chlorine. 

102.  The  addition  of  ammonium  sulphide  to  a  solution  of 
a  manganous  salt  precipitates  manganous  sulphide,  MnSjHjO. 
This    precipitate   is   salmon   colored,   but    turns   dark   upon 
e.Yno»ure  to  the  air.     It  is  insoluble  in  alkalies  and  soluble  in  ^"^* 
dilute  acids.     On  heating,  it  sometimes  turns  green  through 

loss  of  water,  after  wljich  change,  it  has   the  composition 
represented  by  the  formula,  MnS. 

103.  The  addition  of  ammonia  to  a  solution  of  a  man- 
ganou.'  salt  throws  down  manganous  hydrate,  Mn(OH)a,  a 
white  precipitate,  which  rapidly  absorbs  oxygen  from  the  air 

and  turns  brown.     If  the  solution  contains  much  ammonium  Mn(OH),. 
salt,  ammonia  produces  no  precipitate  at  first.      Potassium 
and  ammonium  hydrates  react  in  the  same  way  as  ammonia. 

104.  The  addition  of  chlorine  or  bromine  water  to  a  solu- 
tion of  manganous  acetate  throws  down  all  the  manganese,  as 
hydrated  manganese  peroxide,  MnO(OH)2. 


MnO< 


xStb* 


mST" 


."-^ 


26 


REACTIONS  OF  THE  BASES. 


[§>>! 


S 

51: 


*.  r. 


Borax 

bead 

reaction. 


Ni]MnO« 
MnOa- 

HMnO«. 


Blowpipe 
reactions 
of  Zn. 


ZnS. 


Zn(OH),. 


Z05>  Potassium  ferrocys^nide  produces  in  manganese  solu- 
tions a  precipitate  of  mangan>i8e  ferrocyanide. 

1 06.  Manganese  compounds  dissolve  in  the  borax  or 
metaphosphate  bead  (^18),  rendering  it  violet  in  the  oxidizing 
flame,  colorless  in  the  reducing  flame. 

X07.  Manganese  compounds  when  fused  with  a  soda  bead 
in  the  oxidizing  flame,  color  it  bright  apple-green,  from  the 
formation  of  sodium  manganate,  NajMnOi.  If  the  bead  be 
dissolved  in  water  and  then  boiled  with  a  drop  of  alcohol, 
brown  flocks  of  manganese  peroxide  separate. 

108.  If  a  manganese  compound  be  warmed  with  concen- 
trated nitric  acid  and  lead  peroxide,  PbOj  (or  a  fragment  of 
potassium  chlorate),  the  solution  will  turn  violet,  from  the 
formation  of  permanganic  acid,  HMnO^.  This  reaction  is 
extremely  delicate. 

ZINC,  Zn  ■>• 

109.  Zinc  is  a  white,  crystalline  metal,  which  dissolves 
slowly,  when  pure,  in  dilute  acids,  forming  colorless  salts 
which  have  an  astringent  taste.  The  metal,  or  its  oxy-salts, 
when  heated  in  the  oxidizing  flame,  give  a  film  of  zinc  oxide, 
ZnO,  yellow  when  hot,  white  when  cold.  If  this  film  be 
moistened  with  a  dilute  solution  of  cobaltous  nitrate,  and  then 
intensely  heated  in  the  oxidizing  flame,  it  becomes  green. 

110.  Zinc  is  precipitated  from  solutions  of  its  salts,  on  the 
addition  cf  ammonium  sulphide,  a  "-nc  sulphide,  ZnS,  a  color- 
less, pasty,  flocculent  or  gelatinous  precipitate,  which  is  readily 
soluble  in  cold  and  dilute  acids,  except  acetic,  insoluble  in 
ammonia  and  the  alkalies. 

Zinc  sulphide  gives  the  blowpipe  reactions  described  in  the 
foregoing  paragraph.  ,,       i_ 

111.  Ammonia,  potassitim  hydrate  and  sodium  hydrate 
produce,  in  solutions  of  zinc  salts,  a  colorless,  amorphous 
precipitate  of  zinc  hydrate,  Zn(OH)j,  which  very  readily 
dissolves  in  an  excess  of  the  precipitant.  The  addition  of 
ammonium  sulphide,  or  hydrogen  sulphide,  to  such  an  alkaline 
solution,  precipitates  the  zinc  as  zinc  sulphide.  . 


ad 
ca 


th 
oil 


•■  itj:.-.'<>>m!bt'r««,'i,i»j^h<».iij*te-' 


.  ifMHH'tiiitiiia^lilit'.- 


„4~^^* 


•  ». 


T 


1  manganese  solu- 

e. 

in  the  borax  or 
et  in  the  oxidizing 

d  with  a  soda  bead 
le-green,  from  the 
^.  If  the  bead  be 
i\  drop  of  alcohol, 
ite. 

irmed  with  concen- 

,  (or  a  fragment  of 

•n  violet,  from  the 

This  reaction  is 


tal,  which  dissolves 
nin"   colorless  salts 
etal,  or  its  oxy-salls, 
a  film  of  zinc  oxide. 
Id.     If  this  film  be 
ous  nitrate,  and  then 
becomes  green. 
IS  of  its  salts,  on  the 
ilphide,  ZnS,  a  color- 
itate,  which  is  readily 
:  acetic,  insoluble  in 

tions  described  in  the 

and  sodium  hydrate 
colorless,  amorphous 
which  very  readily 
nt.  The  addition  of 
le,  to  such  an  alkaline 
phide. 


§>>61 


BASES  OF  THE  FIFTH  GROUP. 


37 


Solubility 


112.  Potassium  ferrocyanide,  produces  a  white  crystalline 
precipitate  of  zinc  ferrocyanide  (ZnjKjFei(CN)ij),  even  in 
very  dilute  solutions  of  zinc  salts. 

GROUP  V. 
SILVER,  MERCURY.  LEAD,  COPPER,  BISMUTH,  CADMIUM. 

113.  The  bases  of  this  group  are  precipitated  by  hydro- 
gen sulphide  from  neutral,  alkaline  or  slightly  acid  solution,  as 
sulphides. 

These  sulphides  are  black,  except  cadmium  sulphide,  which 
is  yellow,  and  are  insoluble  in  ammonium  sulphide.  Sodium 
carbonate  precipitates  the  bases  -of  this  group  as  carbonates 
or  basic  carbonates. 

SILVER,  Ag' or  (Agj)". 

X  Id.     Silver  is  insoluble  in  dilute  sulphuric  or  hydrochloric 
acids,  soluble  in  nitric  acid,  and  m  hot,  concentrated  sulphuric  ^^  ^^ 
acid,  forming  colorless  salts. 

115.  Solutions  of  a  silver  salt  give  with  hydrogen  sul- 
phide a  black  precipitate  of  silver  sulphide,  AgjS;  insoluble  in 
dilute  acids  and  alkalies ;  soluble,  with  decomposition,  in  boil-  AgjS. 
ing  concentrated  nitric  acid.     On  charcoal  it  is  readily  reduced 

(§12)./         ;'-,-.,.,.--"-       :.  ^       - 

116.  Solutions  of  silver  salts  are  thrown  down  by  hydro- 
chloric acid,  or  a  soluble  chloride,  as  silver  chloride,  AgjClj,* 
a  white,  curdy  precipitate,  the  separation  of  which  is  facilitated 
by  shaking  and  by  acidification  with  nitric  acid.  It  becomes 
violet  or  black  when  exposed  to  the  light.  It  is  insoluble  in 
acids  and  in  sodium  or  potassium  hydrates,  readily  soluble  in 
ammonia,  and  in  solutions  of  sodium  thiosulphate  or  potassium      '    '' 

iodide. 

From  these  solutions  it  may  again  be  thrown  down  by  the 
addition  of  nitric  acid.  When  fused  on  charcoal  with  sodium 
carbonate  (§12)  it  is  readily  reduced  to  globules  of  silver. 


>  Also  written  AgCl.  It  U  not  settled  whether  all  .'.he  salts  of  silver  contain 
the  double  atom,  ( Ag,)" ,  or  not.  Their  formulas  are  so  written  In  the  text  in 
order  to  exhibit  more  clearly  their  analogy  with  mercurous  and  cuprous  salts. 


f 


t 


r 


SN, 


*H 


■-  t' 


.    i  i'^--     Xk.    .st-^i  . 


0SI 


V'ff 


'•i: 


i 

is 


vt» 


28 


REACTIONS  OF  THE  BASES. 


123 


AgjBra 

and 

Agjij. 


AgjO. 


117.  For  the  reactions  of  silver  salts  with  iodides  and 
bromides  see  §§270,  273,  276. 

118.  All  silver  compounds  are  reduced  readily  to  the 
Reduction,  metallic  state,  when  fused  on  charcoal  with  sodium  carbonate. 

119.  Silver  solutions,  when  warmed  with  tartaric  acid 
and  ammonia,  are  reduced.  The  silver  is  deposited,  partly  in 
the  form  of  a  metallic  mirror  on  the  sides  of  the  test  tube, 
partly  as  a  gray  powder  of  finely  divided  metal. 

120.  The  cautious  addition  of  amtnonia  to  the  solution  of 
a  silver  salt  throws  down  a  brown  or  black  precipitate  of 
silver  hydrate,  Ag2(OH)2,  or  silver  oxide,  AgjO;  easily  solu- 
ble in  excess  of  ammonia. 


MERCURY,   Hg  »  and  (Hg,)"- 

121.  Mercury  is  the  only  metal  which  is  liquid  at  ordinary 
temperatures.  It  dissolves  in  concentrated,  hot  sulphuric 
acid,  or  in  dilute  nitric  acid,  forming  colorless  mercuric  sul- 
phate, or  mercurous  nitrate,  respectively.  Mercurous  salts 
may  be  converted  into  mercuric  salts  by  warming  with  con- 
centrated nitric  acid,  or  hydrochloric  acid  and  potassium 
chlorate. 

Hg2(N03)a  +  3HNO8  =  2Hg(N08)2  +  H2O  +  NA 

Many  mercuric  salts  are  decomposed  by  water,  a  basic  salt 
(usually  yellow)  being  formed  and  a  part  of  thr  acid  being 
set  free. 

3HgS04  +  2H2O  =  ilggOaSOi  +  2H2SO4 

All  mercury  salts  are  volatile  at  high  temj>eratures. 


Salts  of 
Hg. 


(Hgj)  "•  Mercurous  Compounds.  - 

Precioita-  122.  Hydrogen  sulphide  produces,  in  a  solution  of  a  mer- 
tion  with  curous  salt,  a  black  precipitate,  consisting  of  mercuric  sulphide 
HjS.  mixed  with  metallic  mercury, 

Hg2(N08)2  +  HjS  =  HgS  +  Hg  +  2HNO8 
1 23*     A  solution  ot  a  mercurous  salt  gives,  with  hydrochlo- 
Hb  CI       "^  ^^'^  °'"  ^  soluble  chloride,  a  white,  curdy  precipitate  of 
mercurous  chloride,  Hg2Cl2. 

This  precipitate  does  not  change  color  upon  exposure  to  the 


111; 


^<^»^-.  'ij,:jait.^cmiS^Si^ii»<mf^ii^^fi^>i'^^ 


^■: 


J.  1§'23 

ilts  with  iodides  and 

duced  readily  to  the 
ith  sodium  carbonate. 
;d  with  tartaric  acid 
is  deposited,  partly  in 
ides  of  the  test  tube, 
i  metal. 

ania  to  the  solution  of 
r  black,  precipitate  of 
le,  AgaO;  easily  solu- 

ch  is  liquid  at  ordinary 
itrated,  hot  sulphuric 
:.olorless  mercuric  sul- 
'^ely.  Mercurous  salts 
)y  warming  with  con- 
;   acid   and    potassium 

),),  +  H2O  +  N2O4 
i  by  water,  a  basic  salt 
part  of  thf  acid  being 

O4  +  2H2SO4  < 

1  temperatures. 

JNDS.  ••»•■  ■ 

Sj  in  a  solution  of  a  mer- 
ing  of  mercuric  sulphide 

-  Hg  +  2HNO3 

lit  gives,  with  hydrochlo- 

lite,  curdy  precipitate  of 

)lor  upon  exposure  to  the 


§'29l 


BASES  OF  THE  FIFTH  GROUP. 


»9 


Hgu- 


HgS. 


light.   It  is  insoluble  in  dilute  acids,  but  soluble  in  concentrated, 
hot  nitric  acid. 

HgaCla  +  4HNO8  =  HgCla  +  Hg(N08)2  +  HjO  +  Na04 

It  is  insoluble  in  ammonia,  which  turns  it  black» 

Mercuric  Compounds. 

124.  Solutions  of  mercuric  salts  react  with  hydrogen  sul- 
phide, forming  a  black  precipitate  of  mercuric  sulphide,  HgS, 
which  is  insoluble  in  boiling,  concentrated  nitric  acid,  but  solu- 
ble in  rt^«rt  rcjo"/a. 

125.  The  addition  of  a  small  amount  of  stannous  chloride, 
SnCU,  to  a  solution  of  a  mercuric  salt,  produces  a  white,  curdy 
precipitate  of  mercurous  chloride  (§123). 

2HgCl2  +  SnCl2  =  HgjCla  +  SnCU 
An  excess  of  stannous  chloride  reduces  the  mercury  to  the 
metallic  state,  forming  a  grayish  black  precipitate. 
HgCla  +  SnCla  =  SnCl*  +  Hg 

126.  If  a  drop  of  a  mercuric  solution  be  rubbed  on  a 
bright  piece  of  copper,  the  latter  will  become  covered  with 
a  sUvery  coating  of  mercury. 

';       Hg(N08)2  +  Cu  =  Cu(N03)2  +  Hg 

Mercurous  solutions  give  a  similar  reaction. 

If  a  drop  of  a  mercury  solution  be  placed  upon  a  gold  coin, 
and  the  gold  be  touched  with  a  zinc  rod  immeri^ed  in  the  drop, 
metallic  mercury  will  be  deposited  on  the  gold  as  a  white  stain. 

127.  If  a  mercuric  compound  be  mixed  with  perfectly 
dry  sodium  carbonate,  and  strongly  heated  in  a  matrass  (§14), 
a  gray  film  will  form  in  the  upper  part  of  the  tube.  Under 
the  microscope,  this  film  may  be  seen  to  consist  of  globules  of 
mercury.  If  a  fragment  of  iodine  be  then  introduced  half  way 
down  the  tube,  and  gently  warm„d,  the  film  will  become 
bright  red,  from  the  formation  of  mercuric  iodide. 

128.  Solutions  of  mecuric  salts  are  not  precipitated  by 
hyirochloric  acid. 

LEAD,  Pbn*'v- 

129.  Metallic  lead  is   a  very  soft,  bluish  white  metal,  pb  and  Its 
which  dissolves  in  nitric  acid  to  form  lead  nitrate,  Pb(N08)2.  o«WeD. 


SnCI)  and 
mercuric 

salts. 


Amalga- 
mation 
test. 


Reaction 
with 

NajCOa  In 
a  matrass. 


if 


I     1" 


i    -I 


I     ? 


Ak 


'%'-   ■:  — 


-!#«■ 


^^0^' 


|0 


REACTIONS  OF   THE  BASES. 


[§'35 


il; 


i: 


n 


PbS. 


PbSO«. 


PbClj 


Pbl, 


PbCrO«. 


The  metal,  when  heated  in  an  oxidizing  flame,  is  converted 
into  lead  oxide,  PbO,  which  appears  as  a  brownish  coating  on 
the  charcoal. 

The  higher  oxides  of  lead,  minium,  Pb804,  and  lead  per- 
oxide, Pb02,  are  decomposed  by  hydrochloric  acid,  chlorine 
being  set  free  and  lead  chloride,  PbCl2,  formed. 

130.  Solutions  of  lead  salts  give  a  brownish  black  pre- 
cipitate of  lead  sulphide,  PbS,  when  treated  with  hydrogen 
sulphide.  This  precipitate  is  decomposed  and  dissolved  by 
boiling,  concentrated  nitric  acid. 

131.  Solutions  of  lead  salts  give  with  dilute  sulphuric  acid 
a  white,  micro-crystalline  precipitate  of  lead  sulphate,  PbSO*. 
This  precipitate  is  very  slightly  soluble  in  water  and  dilute 
acids.  It  is  readily  soluble  in  a  solution  of  the  hydrates  of 
sodium  or  potassium,  or  in  a  concentrated  solution  of  ammo- 
nium acetate.  It  is  blackened  by  ammonium  sulphide  and,  on 
charcoal,  it  may  readily  be  reduced  to  metallic  lead.  The 
precipitate  does  not  appear  in  very  highly  diluted  solutions. 

132.  The  addition  of  hydrochloric  acid  to  a  concentrated 
lead  solution  produces  a  colorless,  crystalline  precipitate  of 
lead  chloride.  This  compound  is  moderately  soluble  in  cold 
water,  more  readily  in  boiling  water. 

133*  Potassium  iodide  produces  in  neutral  lead  solutions, 
which  are  not  too  dilute,  a  precipitate  consisting  of  beautiful 
golden  yellow  spangles.  This  reaction  is  characteristic  but 
not  delicate. 

134'  "^^^  addition  of  potassium  chromate,  K^CrO^,  or 
pyrochromate,  KaCrjO;,  produces  in  neutral  lead  solutions,  or 
in  those  which  are  acidified  by  acetic  acid,  a  vivid  yellow  pre- 
cipitate of  lead  chromate,  PbCr04,  which  is  somewhat  soluble 
in  dilute  acids,  nearly  insoluble  in  acetic  acid,  and  which  is 
turned  orange  by  ammonia. 

135'  Lead  compounds,  when  fused  with  sodium  carbon- 
ate on  charcoal  in  the  reducing  flame  (§12),  yield  globules  of 
metallic  lead,  which  are  readily  recognized  by  their  physical 
properties. 


M 


'-H4A7  '.\^<4^t:.;'^''fal&h---'fm<»I^S»t^. : 


■3«ft,S!it'i^, 


lS.»i-«iJ*«s-. 


EaM 


18' 3S 

flame,  is  converted 
trownish  coating  on 

bgO*,  and  lead  per- 

iloric  acid,  chlorine 

rmed. 

rownish  black  pre- 

ited  with  hydrogen 

i  and  dissolved  by 

dilute  sulphuric  acid 
ad  sulphate,  PbSO*. 
in  water  and  dilute 

of  the  hydrates  of 
i  solution  of  ammo- 
um  sulphide  and,  on 
metallic  lead.     The 

diluted  solutions, 
cid  to  a  concentrated 
alline   precipitate  of 
ately  soluble  in  cold 

leutral  lead  solutions, 

)nsisting  of  beautiful 

is  characteristic  but 

iromate,  KiiCr04,  or 
tral  leafl  solutions,  or 
i,  a  vivid  yellow  pre- 
1  is  somewhat  soluble 
c  acid,  and  which  is 

[  with  sodium  carbon- 
,12),  yield  globules  of 
ized  by  their  physical 


J«4»l 


BASES  OF  THE  FIFTH  GEO  UP. 
COPPER,  Cu»- 


136.  Copper  is  a  soft  metal  of  characteristic  color,  which 
on  being  heated  in  the  air  forms  the  black  oxide,  CuO.  It  is 
insoluble  in  dilute  hydrochloric  and  sulphuric  acids.  It  is 
readily  oxidized,  and  then  dissolved,  by  dilute  nitric  acid  or  by 
boiling  concentrated  sulphuric  acid.  Cupric  salts  containing 
water  of  crystallization  are  usually  blue  or  green.  Cuprous 
salts  are  generally  colorless.  They  are  not  likely  to  be  met 
with  in  an  analysis,  since  they  rapidly  become  oxidized,  form- 
ing cupric  sahs;  therefore  only  the  latter  will  be  considered 
here. 

137.  Hydrogen  sulphide  precipitates  the  copper  from  its 
salts  as  copper  sulphide. 

CUSO4  +  HaS  =  CuS  +  H2SO4 
Copper  sulphide  is  a  brownish  black  precipitate,  which  is 
somewhat  soluble  in  moderately  concentrated  hydrochloric 
acid,  so  that  care  should  be  taken  to  have  the  solution,  from 
which  copper  sulphide  is  to  be  precipitated,  only  slightly  acid. 
It  dissolves  readily  in  warm,  concentrated  nitric  acid. 

138.  The  addition  of  a  little  ammonia,  to  a  solution  of 
a  copper  salt,  throws  down  copper  hydrate,  Cu(OH)2,  as  a 
pale  blue  precipitate,  which  dissolves  easily  in  an  excess  of 
ammonia  to  a  deep  blue  solution. 

139.  Sodium  or  potassium  hydrate  throws  down,  from  a 
solution  of  a  copper  salt  a  blue  precipitate  of  copper  hydrate, 
which  is  not  soluble  in  an  excess  of  the  precipitant.  If  the 
sodium  hydrate  be  added  in  excess,  and  the  solution  boiled, 
the  precipitate  changes  into  copper  oxide,  at  the  same  time 
tiu-ning  black. 

140.  Potassium  ferrocyanide  produces  in  neutral  or  acid 
solutions  of  copper  salts,  a  brick -red  precipitate,  which 
consists  (,f  copper  ferrocyanide,  Cu2Fe(CN)6,  or  of  copper 
potassium  ferrocyanide,  Cu8K2Fea(Cu)i2,  according  to  the 
conditions  .of  the  precipitation. 

141.  If  potassium  iodide  be  added  to  a  neutral  or  slightly 
acid  solution  of  a  copper  salt,  the  solution  will  turn  brown, 


-' 

ai 

■:      -if 

.*£ 

hf 

Solution 

•  5' 

of  copper. 

1 

f 

4 

1 

Salts  of 

1 

copper. 

CuS. 


Cu(OH), 
dissolves 
in  ammo- 
nia. 


Conversion 
ofCu(OH)j 
into  CuO. 


Ferrocyan- 
ide test 
for  Cu. 


I 


Cujij. 


* 

i 


M-4^:L,ri.t«  J,  >:M'iiI^^m  ■■ 


0 


if^ 


i 


: 


u 


W 


:i 


K: 


3a 


REACTIONS  OF   THE  BASES. 


[§148 


from   the  separation   of  free   iodine,  a  white   precipitate  of 
cuprous  iodide  appearing  at  the  same  time. 

2CUSO4  +  4KI  =  Cual,  +  2KaS04  +  L. 
This  reaction  is  not  very  delicate. 

142.  The  addition  of  sulphurous  acid  (or  a  sulphite)  and 
potassium  sulphocyanate  to   the   solution  of  a  copper  salt, 

Cu,(SCN)j.P*'o<^"ces  a  curdy,  white,  amorphous  precipitate  of  cuprous 
sulphocyanate,  insoluble  in  dilute  acids. 

2CuCl,  +   2KSCN    +    HjSOb  +   HjO   = 
Cu2(SCN)2   +    H2SO4   +    2HCI   +    2KCI 

143.  Globules  of  metallic  copper  are  readily  obtained, 
when  a  copper  compound  is  reduced  with  sodium  carbonate 
on  charcoal  (§12,  see  note). 

144.  The  borax  bead  is  colored  blue  by  copper  com- 
pounds in  the  oxidizing  flame.  In  the  reducing  flame  the 
bead  becomes  red  and  opaque.  The  latter  reaction  is  aided 
by  the  addition  to  the  bead  of  a  little  stannic  oxide,  or  tin  foil. 

145.  Oxy-salts  of  copper  impart  to  the  flame  an  emerald- 
green  coloration.  Haloid  salts  of  the  same  metal  color  the 
flame  blue. 

146.  A  bright  piece  of  steel  or  iron,  when  plunged  into  a 
neutral  or  slightly  acidified  solution  of  a  copper  salt,  becomes 
coated  with  metallic  copper. 

BISMUTH,  Bi 'I- 


Reduction 
of  Cu. 


Cu  in  the 
borax  bead 


Flame 
coloration 

Iron  test 
for  Cu. 


BijOa. 


Basic  salts 
of  Bi. 


Bi,S,. 


147.  Bismuth  is  a  brittle,  reddish  white  metal,  which,  in 
the  oxidizing  flame,  is  converted  into  bismuth  oxide  BijOa, 
which  forms  a  yellow  incrustation  on  the  charcoal,  brown 
while  hot.  It  is  insoluble  in  dilute  hydrochloric  and  sulphuric 
acids,  but  soluble  in  dilute  nitric  acid.  Normal  bismuth  salts 
are  readily  decomposed  bj-^  water,  especially  in  boiling,  form- 
ing insoluble  basic  salts.  ;    >< 

148.  Hydrogen  sulphide  precipitates  bismuth  from  its 
solutions  as  bismuth  sulphide,  BiaSg,  insoluble  in  dilute  acids, 
but  readily  dissolved,  with  decomposition,  by  boiling  nitric 
acid. 


C£| 

tV 


bit 


i '.  •?^ ! 


■"  wW«-«t- iii*iCi*^W*l^»- 


t,.-  MOMii 


T 


[§>48 
lite   precipitate  of 

(or  a  sulphite)  and 

of   a  copper   salt, 

cipitate  of  cuprous 

+   H,0   = 

:i  +  2KCI 

e  readily  obtained, 
1  sodium  carbonate 

ie  by  copper  corn- 
reducing  flame  the 
ter  reaction  is  aided 
nic  oxide,  or  tin  foil, 
le  flame  an  emerald- 
ime  metal  color  the 

when  plunged  into  a 
copper  salt,  becomes 


hite  metal,  which,  in 
bismuth  oxide  BiaOa, 
the  charcoal,  brown 
)chloric  and  sulphuric 
'formal  bismuth  salts 
ially  in  boiling,  form- 

tes  bismuth  from  its 
jluble  in  dilute  acids, 
ion,  by  boiling  nitric 


8'S61 


BASES  OF  THE  FIFTH  GROUP. 


33 


Bi,02- 


149.  If  a  bismuth  solution,  containing  but  httle  free  acid, 
be  treated  with  a  small  quantity  of  hydrochloric  acid,  then 
diluted  with  much  water  and  boiled,  a  precipitate  of  bismuthyU 
chloride,  (BiO)Cl,  will  be  thrown  down. 

150.  Ammonia,  potassium  hydrate,  or  sodium  hydrate' 
throw  down  from  bismuth  solutions  a  white  precipitate  of  bis- 
muthyl  hydrate,  (BiO)OH,  insoluble  in  alkalies.         \ 

151.  Potassium  p)rrochromate  precipitates  bismuth  chro- 
mate,  Bi2(Cr04)8,  as  a  yellow  powder,  from  bismuth  solutions 
which  do  not  contain  too  much  free  acid.  This  precipitate 
dissolves  in  dilute  nitric  acid. 

152.  If  to  a  solution  of  bismuth,  stannous  chloride  be 
added  and  then  sodium  hydrate  in  excess,  the  bismuth  will  be 
thrown  down  as  bismuthous  oxide,  BijO),  a  black  precipitate. 
This  is  the  best  reaction  for  the  detection  of  bismuth  com- 
pounds. 

2Bi(N08)8  +  SnCla  -H  8NaOH  = 
BiaOa  +  dNaNOg  +  aNaCl  +  NaaSnOg  +  4HaO 

153.  With  sodium  carbonate  on  charcoal,  bismuth  com- 
pounds can  be  reduced  before  the  blowpipe,  to  brittle  globules 
of  metallic  bismuth. 

154.  If  a  bismuth  compound  be   mixed   with  a  little 
sulphur  and  potassium  iodide,  and  the  mixture  heated  on  char- 
coal, a  scarlet  incrustation  of  bismuth  iodide  will  be  formed  on  < 
the  support.    The  same  reaction  may  with  advantage  be  car- 
ried out  in  the  closed  tube  or  matrass. 

CADMIUM,  Cd"- 

155.  Cadmium    is  a   silvery   white,   malleable,  volatile  qj 
metd,  which  readily  bums  in  the  oxidizing  flam>j,  forming 
cadmium  oxide,  CdO,  which  produces  a  brown  incrustation  on 
the   support.     The   metal   dissolves  in   dilute  hydrochloric, 
nitric,  or  sulphuric  acids,  forming  colorless  salts. 

156.  Hydrogen  sulphide  precipitates  from  solutions  of 
cadmium  salts  cadmium  sulphide,  CdS,  as  a  bright  yellow 


BIOCI. 


(BIO)OH. 


Bl^CrO*),. 


Reduction 
of  Bi. 


Blowpipe 
test  for  Bi. 


CdS. 


•Tin  -mivalent  radical  (BIO/  which  occurs  in  many  compounds,  is  called 
bismuthyl. 


4 


•  % 


'a. 

•    .*• 

.J     ~r 


%l 


W  -fH 


^  da#»«^^r— 


Ik 


MJt 


34 


KB  ACTIONS  OF  TUB  BASSS. 


[§'59 


precipitate,  which  is  insoluble  in  cold,  dilute  acids,  and  in 
potassium  cyanide.     It  is  readily  decomposed  and  dissolved  by 
boiling  nitric  acid  and  also  by  boiling  dilute  sulphuric  acid. 
f'cdS  °"  '^^^  latter  reaction  may  be  used  to  separate  cadmium  sulphide 
from  CuS.  ^o™  copper  sulphide.     Cadmium  sulphide  cannot  be  precipi- 
tated from  a  solution  which  contains  much  hydrochloric  acid. 
1 57*     Ammonia  precipitates  from  cadmium  solutions  white 
Cd(OH),.  cadmium  hydrate,   which  easily  dissolves  in   an   excess  of 
ammonia. 

GROUP  VI. 
TIN,  ARSENIC.  ANJIMONY,  (GOLD,  PLATINUM). 

158.     Metals  of  this  group  are  precipitated,  as  sulphides, 

from  acid  solutions  of  their  salts  by  hydrogen  sulphide;  and 

their  sulphides  are  soluble  in  ammonium  sulphide.^ 

OxideBof      Their  lower  oxides  (SnO,  AsjOg*,  SbjOg)  act  as  bases, 

metals  of  ^^ile  their  higher  oxides  (SnOj,  AsjOs,  SbjOs)  exhibit  the 

'deportment  of  anhydrides,  that  is,  in  combination  with  water 

they  form  acids,  with  bases,  salts. 


TIN,  Sn""*''. 

159'  T'"  '8  a  malleable,  silvery  white  metal,  which  does 
not  tarnish  and  which  is  but  little  attacked  by  dilute  sulphuric 
acid.  It  dissolves  readily  in  warm,  concentrated  hydrochloric 
acid,  with  difficulty  in  the  diluted  acid,  to  form  a  colorless 
properties  solution  of  Stannous  chloride.  Concentrated  nitric  acid  con- 
ofUn.  verts  it,  with  the  evolution  of  brown  fumes,  into  insoluble 
metastannic  acid,  H^SnOs.  It  dissolves  in  cold,  dilute,  nitric 
acid,  as  stannous  nitrate,  Sn(N08)2. 

Stannous  salts  are  converted  into  stannic  salts  by  agua  regi'a 
and  by  other  oxidizing  agents.  In  the  oxidizing  flame,  tin  is  very 
easily  oxidized  to  stannic  anhydride,  SnOj,  a  yellowish  white 

>The  ammonium  sulpliide  referred  to  Iiereis  a  solution  of  the  salt  wtiich  lias 
become  yellow  by  keeping,  or  by  the  addition  of  sulphur,  and  which,  therefore, 
contains  some  ammonium  poly-sulphide,  such  as  (NH«)2S3  or  (NH4)3Sg,  etc. 

*Thi6  oxide  acts  both  as  an  anhydride  and  as  a  base. 


ill  J 


!.«a  <i*St^w  /i:-'i*lKi*»felSife^^-'^-' 


,j*.». 


7^:it^;^MS~ 


I 


umiiP 


jll 


J\ 


»'59 

ilute  acids,  and  in 
;d  and  dissolved  by 
ate  sulphuric  acid. 
!•  cadmium  sulphide 
cannot  be  precipi- 
hydrochloric  acid, 
lium  solutions  white 
s  in  an  excess  of 


PLATINUM). 

►itated,  as  sulphides, 

rogen  sulphide;  and 

lulphide.^ 

JbjOa)  act  as  bases, 

,  SbjOfi)  exhibit  the 

nbination  with  water 


e  metal,  which  does 
d  by  dilute  sulphuric 
jntrated  hydrochloric 

to  form  a  colorless 
rated  nitric  acid  con- 
fumes,  into  insoluble 

in  coiS,  dilute,  nitric 

lie  salts  by  agt4a  re^'a 
dizing  flame,  tin  is  very 
Oj,  a  yellowish  white 

alution  of  the  salt  which  has 
jlphur,  and  which,  therefore, 
:NH4>,Saor(NH«)jS„etc. 

ase.  ■"■1^ 


i'63l 


BASES  OF  THE  SIXTH  GROUP. 


35 


powder,  which  is  infusible  and  non-volatile,  and  which  becomes 
greenish  blue  when  moistened  with  cobaltous  nitrate  and  then 
strongly  ignited. 

1 60.  Acid  solutions  of  stannous  salts  give  with  hydrogen 
sulphide  a  brown  precipitate,  consisting  of  a  compound  of 
stannous  sulphide,  SnS,  with  water.  This  precipitate  becomes 
black  when  dried.  The  addition  of  hydrogen  sulphide  to  an 
acid  stannic  solution  producee  a  yellow  precipitate,  consisting 
of  a  mixture  of  stannic  sulphide,  SnS2,  and  stannic  anhydride, 
SnOj. 

Both  of  these  precipitates  dissolve  in  yellow  ammonium  sul- 
phide. If  either  of  the  solutions  so  obtained  be  acidified  with 
hydrochloric  acid,  the  tin  is  precipitated  as  yellow  stannic 
sulphide,  SnSj. 

161.  The  tin  may  be  entirely  precipitated  from  either  a 
stannous  or  stannic  solution  as  metastannic  acid,  HjSnOg,  by 
prolonged  boiling  with  an  excess  of  nitric  acid. 

162.  Solutions  of  stannous  salts  have  a  powerful  reduc- 
ing action.  They  will  therefore  decolorize  starch  paste,  which 
has  been  made  blue  by  the  addition  of  a  little  iodine  solution; 
they  will  change  the  red  color  of  a  mixture  of  potassium 
pyrochromate  and  sulphuric  acid  to  a  green  (§222);  they 
will  turn  blue  a  mixture  of  ferric  sulphate  and  potassium 
ferricyanide  {%^)',  they  will  precipitate  mercurous  chloride 
from  a  solution  of  mercuric  chloride  (§125).  The  last  men- 
tioned of  these  reactions  is  the  most  generally  applicable  and 
characteristic.  ■   .' 

163.  If  a  solution  of  a  stannic  salt  is  neutralized  with 
ammonia,  potassium  hydrate,  sodium  hydrate,  or  with  a  car- 
bonate, a  gelatinous  precipitate  of  stannic  acid,  HjSnOg,  is 
formed,  which  is  readily  soluble,  in  acids  to  form  stannic  salts, 
in  alkalies  to  form  stannates. 

HjSnOs  +  4HCI  =  SnCU  +  sHaO 
HjSnOa  +  2NaOH  =  NaaSnOg  +  2HaO 

Under  certain  conditions,  which  are  imperfectly  understood, 
stannic  acid  changes  into  metastannic  acid,  which  has  the  same 
composition,  but  is  insoluble  in  acids. 


SnS. 


SnSi 


Precipita- 
tion of 
HjSnO,. 


Reducing 
action  of 
stannous 
compounds. 


Stannic 
acid. 


i 


I 

'4 


I 

i 


Vi 


Ht 


1^  \ 


,  fc    1,         -.  -     }•. 


36 


REACTIONS  OF  THE  BASES. 


[§>67 


;mi 


1 64*    Ha  fragment  of  zinc  be  introduced  into  an  acidiBed 

o*Sn*^wUh***""'^  solution,  the  latter  will  be  reduced,  first  to  a  stan- 

2n,  nous  salt,  and  then  to  metallic  tin,  which  will  be  deposited 

upon  the  zinc,  in  spongy  form  or  in  crystals.     The  deposit 

may  be  dissolved  in  a  little  strong  hydrochloric  acid  and  tested 

according  to  §162.  •    v 

l65>     AH  tin  compounds  can  be  reduced  with  sodium 

jjj g^ ^jj'J^  carbonate  on  charcoal  (§12) •     This  reduction  is  difficult  and 

"Cyanide  requires  the  prolonged  action  of  a  powerful  reducing  flame. 

flux."        Ifj  instead  of  sodium  carbonate,  the  tin  compound  be  mixed 

with  "cyanide  flux"  (v.  note  §12),  the  reduction  to  globules 

of  metallic  tin  is  more  easily  effected. 

SnOa  +  2KCN  =  2KOCN  +  Sn  f 


ARSENIC,  AsW  —  v. 

166.  Arsenic  is  a  brittle,  grayish  white  element  of  metal- 
lic lustre.  It  is  sometimes  classified  as  a  metal,  sometimes 
as  a  non-metal.  Most  of  its  compounds  are  volatile,  and 
all  are  poisonous.  Heated  on  the  charcoal  stick  with  the 
blowpipe  flame,  it  bums  to  arsenous  oxide,  AS2O8,  which 
appears  as  a  white  smoke  and  which  is  partly  deposited  as  a 
volatile  white  film,  at  some  distance  from  the  assay  piece,  a 
characteristic  odor  resembling  that  of  garlic,  being  given  off 
at  the  same  time.  A  fragment  of  arsenic,  when  heated  in  the 
closed  tube  or  matrass,  is  sublimed  and  deposited  as  a  shining 
metallic  mirror  in  the  colder  part  of  the  tube. 

Arsenic  is  readily  oxidized  and  dissolved  by  hot  nitric  acid 
or  by  hot,  concentrated  sulphuric  acid. 

167.  Hydrogen  sulphide  produces,  in  acidified  solutions 
of  arsenous  compounds,  a  canary-yellow,  curdy  precipitate  of 
arsenous  sulphide,  AsjSs,  which  Id  easily  soluble  in  ammonium 
sulphide,  and  which  is  precipitated  from  this  solution  on  acidi- 
fication with  hydrochloric  acid.  '  •      '   r       ,.; 

Arsenic  solutions  (/.  e.  those  containing  pentavalent  arsenic) 
are  precipitated  in  the  same  way  by  hydrogen  sulphide,  but,  in 
this  case,  the  precipitation  is  exceedingly  slow,  one  or  two 
days  being  required,  since  the  arsenic  compound  must  be 


Blowpipe 
reactions 
of  arsenic. 


AsjS),, 


Arsenous 
distinguish- 
ed from 
arsenic 
compounds, 


!  vk*  .1 


Ai^'-W 


« ,  ;'.*v.*ii**>sav«.Ww*<^.'- 


■■;".;„"  %si'A'igiw  »^;-S:;-f«-s.^jjaf  "*•--.''";. 


r^~'crai 


uced  into  an  acidified 
ced,  first  to  a  stan- 
ch will  be  deposited 
■ystals.  The  deposit 
:hloric  acid  and  tested 

educed  with  sodium 
luction  is  difficult  and 
erful  reducing  flame, 
compound  be  mixed 
reduction  to  globules 

N  +  Sn  '  ■■ 


hite  element  of  metal- 
is  a  metal,  sometimes 
inds  are  volatile,  and 
arcoal  stick  with  the 
oxide,  AsjOa,  which 
J  partly  deposited  as  a 
om  the  assay  piece,  a 
garlic,  being  given  off 
lie,  when  heated  in  the 
deposited  as  a  shining 
:  tube, 
lived  by  hot  nitric  acid 

3,  in  acidified  solutions 
w,  curdy  precipitate  of 
y  soluble  in  ammonium 
n  this  solution  on  addi- 
ng pentavalent  arsenic) 
'drogen  sulphide,  but,  in 
ngly  slow,  one  or  two 
tic  compound  must  be 


BASES  OF  THB  SIXTH  GROUP. 


37 


Ag,A»0, 


reduced  to  the  arscnous  condition,  before  precipitation  can  take 
place. 

.    HgAsO,  +  HaS  +  3HCI  =  AsCl,  +  4HaO  -\-  S 
2A8Cla  +  3H:,S  =  As^a  +  6HC1 

168.  If  an  exactly  neutral  solution  of  an  arsenous  com- 
pound is  treated  with  silver  nitrate,  a  bright  yellow  precipitate 
of  silver  arsenite,  AggAsOg,  is  formed,  which  dissolves  easily 
in  acids  or  alkalies.  ^ 

NaaAsOa  +  sAgNOg  =  AgaAsO,  +  sNaNO, 
Since  it  is  difficult  to  make  an  arsenous  solution  exactly 
neutral,  it  is  well  to  proceed  as  follows.     '  ' 

Render  the  solution  slightly  acid  with  nitric  acid  and  pour 
carefully  upon  it,  without  mixing,  a  solution  of  silver  nitrate, 
previously  made  slightly  alkaline  with  ammonia.  Between  the 
two  liquids  there  will  be  a  neutral  zone,  in  v/hich  the  precipi- 
tate will  appear  as  a  yellow  ring.  " 

169.  Boiling  nitric  acid  converts  arsenous  compounds  conversion 
into  arsenic  acid.  "*  arsenous 

As,0.  +  2HNO,  =  2HaAsO,  +  N,Oa  '^J^^' 

Arsenic  acid,  when  neutralized  with  ammonia  and  treated  pounds 
with  silver  nitrate,  according  to  the  method  described  in  the 
foregoing  paragraph,  gives  a  brick-red  precipitate  of  silver 
arsenate,  AgaAsO*;  soluble  in  the  mineral  acids  and  in  ammo- 
nia; nearly  insoluble,  in  dilute  acetic  acid.  For  other  reactions 
of  arsenic  acid,  see  §§215-218. 

170.  If  a  solution  containing  arsenic  be  warmed  with  a 
large  excess  dl  ^:oncentrated  hydrochloric  acid  and  a  piece  of 
tin  foil,  a  brownish  precipitate  of  finely  divided  metallic  arsenic 
will  appear. 

171.  If  an  arsenous  solution  be  acidified  with  hydrochloric 

acid  and  the  mixture  digested  for  some  time  with  a  clean  piece  Reinsch's 
of  copper  foil,  the  latter  wiU  become  covered  with  a  shiny  test  for 
black  coating  of  copper  arsenide.     The  coated  copper  should 
be  thoroughly  washed,  dried,  and  heated  in  the  open  tube 
(§15).     Brilliant,  microscopic  crystals  of  AsaOg  will  form  in 


MM-^MM""' 


iChlorides,  bromides  ind  Iodides,  which  precipitate  silver  nitrate,  interfere 
more  or  less  with  this  test. 


'I 

■'t:; 


■I 

4 


'^1 


^il 


s 


"'  ft 

It 


■<l 


wmmmn 


i\ 


f: 


I'i 


i 


I.! 


-.r 


h'' 


1^ 


ij 


!.,;,■, 


l>  ■■iL-' 


£. 


38 


REACTIONS  OF  THE  BASES. 


[|'74 


Marth'i 

te»t. 


Arsenical 
mirror 
and  upots. 


the  upper  part  of  the  tube.  •  In  case  the  coating  on  the  copper 
should  be  small  in  quantity,  it  would  be  better  to  heat  it  in  a 
closed,  instead  of  an  open  tube,  of  hard  glass,  about  three 
sixteenths  of  an  inch  in  outside  diameter.  The  reason  for  this 
is  that  the  strong  current  of  hot  air  through  the  open  tube 
might  well  carry  of!  and  dissipate  very  small  quantities  of 
arsenic,  an  accident  which  can  not  happen  in  using  a  matrass. 

172.  If  a  very  small  quantity  of  a  ^olution  containing 
arsenic  be  added  to  a  mixture  of  dilute  sulphuric  acid  and 
zinc,  the  escaping  hydrogen  will  contain  arsine,  AsHg,  which 
has  a  very  characteristic  odor.  If  the  gas  be  passed  through 
a  hard  glass  tube,  two  or  three  inches  of  which  are  heated  by 
a  Bunsen  flame,  metallic  arsenic  will  be  deposited  as  a  brilliant, 
brownish  black  mirror,  beyond  the  heated  part  of  the  tube. 
(Compare  §177.) 

If  the  gas,  as  it  escapes  from  the  end  of  the  tube,  is  ignited, 
the  flame  will  bum  with  a  pale  blue  color,  different  from  that 
of  pure  hydrogen,  and  will  emit  an  odor  resembling  that  of 
garlic.  If  a  cold  porcelain  dish  be  held  in  the  flame,  a  brilliant 
black  spot  of  metallic  arsenic  will  be  deposited  upon  it. 

173.  When  an  arsenic  compound  is  heated  in  the  blow- 
pipe flame,  on  charcoal,  the  odor  and  film  mentioned  in  §166 
may  be  observed. 

ANTIMONY,  Sb'"*v- 

174.  Antimony  is  a  brittle,  white  metal  of  high  metallic 
lustre.     When  heated  on  charcoal,  in  the  oxidizing  flame,  it 

I'ropertiet  jj^^ns  with  a  bluish  flame,  depositing  a  white  coating  of  anti- 
mony, monous  oxide,  SbjOg,  on  the  charcoal.  This  film  is  less 
volatile  and  forms  closer  to  the  assay  than  the  analogous 
incrustation  of  arsenous  oxide.  Antimony  is  very  fusible,  and 
much  less  volatile  than  arsenic.  The  metal  is  insoluble  in 
hydrochloric  or  dilute  sulphuric  acids;  dilute  nitric  acid  oxid- 
izes it  to  antimonous  oxide,  SbjOg;  hot  concentrated  nitric  acid 

'Remark:-— Under  the  conditions  given,  a  solution  conUining  antimoHy  will 
produce  a  dull  black  stain  on  the  copper,  but  no  octahedral  crjrstals  can  be 
obtained  hy  subsequent  heating  in  the  tube,  unless  arsenic  is  present. 


'  -Hi..  •.>»r4«-<t,!.'jfc  iMr,»iV%irt!*!;i 


T^:i-uiSW~ 


n 


mating  on  thy  copper 

better  to  heat  it  in  a 

glass,  a^}out  three 

The  reason  for  this 

ough  the  open  tube 

small  quantities  of 

in  using  a  matrass. 

solution   containing 

!  sulphuric  acid  and 

arsine,  AsHj,  which 

IS  be  passed  through 

which  are  heated  by 

;posited  as  a  brilliant, 

ted  part  of  the  tube. 

)f  the  tube,  is  ignited, 
jr,  different  from  that 
or  resembling  that  of 
ii  the  flame,  a  brilliant 
josited  upon  it. 

heated  in  the  blow- 
Im  mentioned  in  §i66 


netal  of  high  metallic 
the  oxidizing  flame,  it 
white  coating  of  anti- 
1.  This  film  is  less 
\f  than  the  analogous 
ny  is  very  fusible,  and 
metal  is  insoluble  in 
dilute  nitric  acid  oxid- 
:oncentrated  nitric  acid 


tlon  conuining  anlimoHy  will 
a  octahedral  crysUls  can  be 
I  arsenic  is  present. 


i.4'^»o 


«'781 


BASES  OF  THE  SIXTH  GROUP. 


39 


Instability 


converts  it  into  metantimonic  acid,  HjSl  Oa,  a  nearly  insoluble 
compound;  aqua  regit  dissolves  it  as  antimonic  chloride,  SbCls. 

175.  Hydrogen  sulphide  precipitates  antimonous  sulphide,    . 
SbfSs,  from  acid  solutions  of  antimonous  compounds,  and  the    - 
same  precipitate,  mixed  with  antimonic  sulphide  (Sb^Sg),  from 
similar  solutions  of  antimonic  compounds.     The  sulphides  of  Sb,s,i. 
antimony  dissolve  in  yellow  ammonium  sulphide.     When  this 
solution  is  acidified  with  hydrochloric  acid,  the  whole  of  the 
antimony  is  thrown  down  as  an  amorphous,  orange  precipitate 
of  antimonic  sulphide,  SbjSs. 

176.  Neutral  or  slightly  acid  solutions  of  antimony  readily 
become  opalescent  and  deposit  a  precipitate,  especially  when  of  unti- 
boiled.     In  the  case  of  antimonic  compounds  this  precipitate  mony 
consists  of  metantimonic  acid,    HSbOg,  in  the  case  of  anti-  «»'""<'"»• 
monous  compounds,  it  consists  of  a  basic  salt,  for  example, 
SbOCl,  antimonyl  chloride.' 

177.  An  antimony  solution,  when  treated  as  described  in 
§172,  forms  a  mirror  or  stains  of  metallic  antimony,  which  dif- 
fers from  the  arsenical  mirror  in  being  soot-black  and  without 
lustre,  when  deposited  directly  from  the  flame  on  a  porcelain 
plate,  but  which  often  posess  a  silvery  lustre  when  formed  in 
a  healed  tube.  In  the  latter  case  the  mirror  sometimes  appears 
on  both  sides  of  the  heated  portion  of  the  tube.  The  escaping 
gas,  when  burnt,  gives  no  odor  of  garlic. 

178.  A.lkaline  solutions  of  antimonous  compounds,  which 

may  be  looked  upon  as  solutions  of  salts  of  the  hypothetical  ^^  gUverbv 
antimonous  acid,  HgSbOg,  precipitate   metallic  silver  from  a  A8,o,. 
solution  of  silver  nitrate.    The  subsequent  addition  of  ammonia 
redissolves  any  silver  oxide,  which  may  have  been  precipitated 
at  the  same  time,  leaving  the  reduced  silver  as  a  fine  black 
powder. 

The  test  can  be  applied,  in  a  modified  form,  directly  to  the 
antimonous  film  obtained  by  heating  antimony  compounds  on 
charcoal  or  in  the  open  tube.    If  such  a  film  be  moistened  with 


'Analogous  to  bismuthyl  chloride,  BiOCl.  Basic  antimony  compounds  may 
be  distinguished  from  those  of  bismuth  by  the  fact  that  the  former  only  are 
soluble  in  tartaric  acid. 


^asSp  rv:»^Bliaj&Sif 


~assr.~ 


wt^. 


REACTIONS  OF  THE  BASES. 


Bt84 


Zinc 

reduction 

test. 


silver  nitrate,  and  then  be  subjected  to  the  action  of  the  vapour 
of  strong  ammonia  water,  it  will  turn  black,  in  consequence  of 
a  reduction  of  the  silver  salt. 

179  If  a  piece  of  platinum  foil  be  immersed  in  a  solution 
of  antimony  acidified  with  hydrochloric  acid,  and  a  piece  of 
zinc  be  placed  in  the  liquid,  in  contact  with  the  foil,  a  sooty 
stain  of  metallic  antimony  will  be  deposited  upon  the  latter. 

This  reaction  distinguishes  antimony  from  the  other  metals 
of  this  group. 

180.  If  an  antimony  compound,, mixed  with  sodium  car- 
bonate and  potassium  cyanide,  be  exposed  to  the  blowpipe 
reducing  flame  on  charcoal,  globules  of  metallic  antimony  will 
be  produced,  which  can  be  recognized  by  the  properties  of 
the  metal  as  given  in  §174,  after  separation  from  the  flux  by 
digestion  with  water. 

PLATINUM,  Pt"«»  "• 


181.  Platinum  is  a  bluish  white,  malleable  metal,  infusi- 
ble in  the  Bunsen  flame;  insoluble  in  nitric  acid,  hydrochloric 
acid,  sulphuric  acid;  soluble  (but  slowly)  in  aqua  regia,  form- 
ing chloro-platinic  acid,  HjPtCU,  which  has  a  deep  orange- 
brown  color  and  which,  upon  evaporation  of  its  solution,  is 
separated  into  hydrochloric  acid  and  platinum  chloride,  PtCl*. 

Reduction.  1 82.  The  salts  of  platinum,  when  heated  to  redness,  are 
decomposed  with  the  separatioii  of  metallic  platinum. 

PtCi,.  183.     A  solution  of  platinum  in  aqua  regia,  or  chloro- 

platinic  acid,  when  added  to  a  solution  of  potassium  chloride, 
throws  down  a  yellow  precipitate  consisting- of   octahedral 

KjPtci..  crystals  of  potassium  chloro-platinate,  KaPtClfl.  In  making 
this  test,  a  drop  of  each  of  the  solutions  should  be  mixed 
upon  a  microscope  slide 

COLO,  Au'*'"-  /> 


Proper- 
tie8  of 
platinum 


Au. 


184.  Gold  is  a  soft,  malleable  metal  of  characteristic 
color,  insoluble  in  hydrochloric,  nitric  and  sulphuric  acids;  but 
readily  soluble  in  aqtia  regia,  as  auric  chloride,  AuCls- 


■'■■'iSi^^am^^hmti^.  -'• 


'% 


i      ' 


T 


[l'84 

action  of  the  vapour 
k,  in  consequence  of 

kmersed  in  a  solution 
acid,  and  a  piece  of 
ath  the  foil,  a  sooty 
sd  upon  the  latter, 
•om  the  other  metals 

ed  with  sodium  car- 
sed  to  the  blowpipe 
netallic  antimony  will 
by  the  properties  of 
on  from  the  flux  by 


§•87) 


BASES  OF  THR  SIXTH  GROUP. 


41 


185.  At  a  red  heat,  the  salts  of  gold  are  decomposed.  Reduction 
the  gold  being  separated  as  a  sponge,  which,  before  the  blow-  ^^  ***"'• 
pipe,  can  be  fused  to  globules  of  metallic  gold. 

186.  If  a  solution  of  ferrous  sulphate,  or  of  oxalic  acid, 

in  excess,  be  added  to  a  solution  of  a  gold  salt,  the  gold  is  ^^  ^^^^ 
reduced  to  the  metallic  state  and  appears  as  a  finely  divided, 
dull  brown  precipitate,  which,  when  dried  and  rubbed,  exhibits 
metallic  lustre. 

187.  If  a  gold  solution  is  treated  with  a  mixture  of  stan-  Purple  of 
nous  and  stannic  chlorides,  a  purple  coloration  or  precipitate  Cawiui. 
appears. 

This  reaction  is  most  delicate.  The  precipitated  substance 
is  called  Purple  of  Cassius^  its  chemical  constitution  being 
unknown.  , ' 


r^ 


alleable  metal,  infusi- 
ric  acid,  hydrochloric 
)  in  aqtta  regia,  form- 
i  has  a  deep  orange- 
tion  of  its  solution,  is 
itinum  chloride,  PtCl*. 
heated  to  redness,  are 
lUic  platinum. 
gm  regia,  or  chloro- 
uf  potassium  chloride, 
isisting-of   octahedral 
KaPtCle.     In  making 
ions  should  be  mixed 


netal  of  characteristic 
nd  sulphuric  acids;  but 
ihloride,  AuClg. 


■  ■  i  /i^^^^^t^^-- '  -" 


! 


• 

t'. 

^. 

tiff: 


CHAPTER  III 


REACTIONS  OF  THE  ACIDS. 


188.  The  more  commonly  occurring  acids  are  divided 
into  five  analytical  groups,  according  to  their  behaviour 
toward  the  group-reagents,  barium  chloride,  silver  nitrate  and 
potassium  acetate.  Some  of  these  groups  are  further  sub- 
divided. The  following  section  presents  a  general  view  of 
the  classification. 

SYNOPSIS  OF  THE  CLASSIFICATION  OF  THE  ACIDS. 

GROUP  I. 
HjSO*.    Sulphates. 

189.  Precipitated  by  barium  chloride  fi-om  solutions  acidi- 
fied with  hydrochloric  acid. 

GROUP  II. 

Precipitated  by  barium  chloride  from  neutral  solutions,  but 
not  from  those  acidified  with  hydrochloric  acid.- 

DIVISION  I.    HaCO,,  HjSO,,  HjCjO«,  HF. 
Carbonates,  Sulphites,  Oxalates,  Fluorides. 
Decomposed  by  concentrated  sulphuric  acid  with 
the  evolution  of  gas. 

DIVISrON  3.     HsCrOi,  H3PO4,  HgAsOi,  H.BO,,  HjStO,. 
Chromates,  Phosphates,  Arsenates,  Borates,  Silicates. 

Evolve  no  gas  with  concentrated  sulpuric  acid. 


»^fc;,--t  ; 


*''iBi^' 


r 


^^^^^ 


UI.     , 

ACIDS. 

ing  acids  are  divided 
r  to  their  behaviour 
»ride,  silver  nitrate  and 
oups  are  further  sub- 
nts  a  general  view  of 

ON  OF  THE  ACIDS. 

5.  ' 

de  from  solutions  acidi- 


n  neutral  solutions,  but 
aric  acid.'  ,' 

HjSOg,  HjCjOi,  HF. 
Oxalates,  Fluorides. 
ated  sulphuric  acid  with 

)„  H,A804,  H,BOg,  HjSIO,. 
sNATEs,  Borates,  Silicates. 
gntrated  sulpuric  acid. 


§'9o] 


CLASSIFICATION  OF  THE  ACIDS. 


GROUP  III. 


Precipitated  by  silver  nitrate  from  dilute  solutions  acidified 
with  nitric  acid.  r;^.  ^  .    ,^^   ,  j,  ,     .  ..     ^  v   ' '," 

*  DIVISION  I.     HSCN,  H^FeQN,,  H,FeC»N,. 

Sulphocyanatbs,  Ferrocyanides,  Ferricyanioes. 

Give  a  red  or  blue  coloration  with  iron  salts. 

DIVISION  2.    HCIO,  HClOa,  HNO„  (Cl„  Br„  I,). 
Hypochlorites,  Chloritbs,  Nitrii  es,  (Free  Haloids.) 

Bleach  indigo  solution. 

DIVISION  3.    HjSaO,,  HjS. 
Thiosulphate^,  Sulphides,  Polysulphides. 

Give  a  black  precipitate  with  silver  nitrate,  either 
at  once  or  on  boiling. 

DIVISION  4.     HCl,  HBr,  HI,  HCN. 
Chlorides,  Bromides,  Iodides,  Cyanides. 

Do  not  give  reactions  of  divisions  i,  2  and  3. 

'^     GROUP  IV. 

'     '      ,  HjC^HtOs,  Tartrates, 

Precipitated  by  potassium  acetate  from  solutions  acidified 
with  acetic  acid.  .  ' 

GROUP  V. 

;/         HOCOCH,,  HClOa,  HNO,. 
Acetates,  Chlorates,  Nitrates. 

Not  precipitated  by  either  of  the  group-reagents. 


m 


GROUP  I.  *       -   t 

SULPHURIC  ACID  AND  SULPHATES,  RjSOt- 

190.     Free  sulphuric  acid,  after  concentration,  will  blacken 
cane  sugar  or  paper  if  heated  to  100°.    If  lines  are  drawn  on    p^gg 
writing  paper  with  water  containing  a  small  quantity  of  free    HjSOi. 
sulphuric  acid,  and  the  paper  be  then  cautiously  dried  and 
heated,  the  lines  will  turn  brown  or  black. 


"t 


is 


)f 


4^. 


T — 


6ls^, 


i» 


44 

BaCI] 

test. 


REACTIONS  OF  THE  ACIDS. 


t§'9S 


Reduction 
test. 


igi.  Barium  chloride  produces,  even  in  extremely  dilute 
solutions  of  sulphuric  acid  or  sulphates,  a  finely  divided,  white, 
crystalline  precipitate  of  barium  sulphate;  nearly  insoluble 
in  dilute  acids  or  alkalies;  soluble  in  hot,  concentrated  sul- 
phuric acid. 

192.  In  applying  the  foregoing  test  for  sulphuric  acid, 
you  must  be  careful  not  to  have  too  much  nitric  or  hydro- 
chloric acid  present,  and  to  make  the  solution  sufficiently 
dilute.  If  strong  nitric  acid  be  added  to  a  solution  of  barium 
chloride,  a  white  precipitate  of  barium  nitrate  appears,  which 
might  be  mistaken  for  barium  sulphate,  and,  similarly,  strong 
hydrochloric  acid  will  precipitate  barium  chloride  from  a  solu- 
tion of  that  salt;  the  reason  for  the  precipitation  being,  in  both 
cases,  the  fact  that  the  salts  named  are  much  less  soluble  in 
strong  nitric  or  hydrochloric  acid  than  in  pure  water. 

193.  Any  sulphate,  when  heated  with  sodium  carbonate 
in  the  reducing  flame,  is  reduced  io  sodium  sulphide,  which  is 
absorbed  by  the  charcoal.  If  the  contiguous  part  of  the  char- 
coal be  dug  out  with  a  pen-knife  blade,  placed  on  a  silver  coin 
and  moistened,  the  silver  will  roon  be  blackened,  from  the 
formation  of  silver  sulphide.  ^ 

NajS  -I-  Ag2  +  HjO  4-  O  =  AgjS  -j-  aNaOH 


Free 
HaSOg. 


GROUP  II. 

DIVISION  T. 
SULPHITES,  CARBONATES,  OXALATES  AND  FLUORIDES. 

194.  This  division  includes  those  acids  which  are  precipi- 
tated by  barium  chloride  in  neutral  but  not  in  hydrochloric 
acid  solutions,  and  which  evolve  a  gas  when  treated  with  con- 
centrated sulphuric  acid. 

Sulphurous  Acid,  and  Suli  .:ites,  RjSOa. 

195.  Free  sulphurous  acid  is  known  only  in  solution.  It 
has  a  strongly  pungent  odor  and  an  acid  reaction.    It  evolves 


»Sulpliites,  thiosulphates  and  all  other  compounds  of  sulphur  give  the  same 
reaction. 


\.-mi 


w, 


,  ^.»"  ^w-- 


T 


i 


[§•95 

in  extremely  dilute 
inely  divided,  white, 
te;  nearly  insoluble 
t,  concentrated  sui- 
tor sulphuric  acid, 
ich  nitric  or  hydro- 
solution   sufficiently 
a  solution  of  barium 
trate  appears,  which 
md,  similarly,  strong 
chloride  from  a  soiu- 
itation  being,  in  both 
nuch  less  soluble  in 
pure  water, 
th  sodium  carbonate 
im  sulphide,  which  is 
lous  part  of  the  char- 
laced  on  a  silver  coin 
blackened,  from  the 


§«99l 


ACIDS  OF  THE  SECOND  GROUP. 


45 


,S  +  2NaOH 


g2' 


S  AND  FLUORIDES. 

ids  which  are  precipi- 
it  not  in  hydrochloric 
?hen  treated  with  con- 


TES,  RjSOa. 

n  only  in  solution.     It 
d  reaction.    It  evolves 


ds  of  sulphur  give  the  same 


iUie 


SOjh  especially  when  warmed,  and  slowly  absorbs  oxygen 
from  the  air,  forming  sulphuric  acid. 

196.  If  a  sulphite  (as  NajSOg)  be  treated  with  sulphuric  •«  bu 
or  hydrochlonc  acid,  the  suffocating  odor  of  sulphurous  acid  paper" 
will  be  evolved.     If  a  strip  of  filter  paper,  previously  moisten- 
ed with  a  solution  of  potassium  ferricyanide  and  ferric  sul- 
phate* be  held  in  the  escaping  vapours,  it  will  turn  blue.* 

Fea(S04)8  +  HaSOg  -}-  HjO  =  2FeS04  +  2HaS04 

197.  If  sulphurous  acid  or  a  sulphite,  be  added   to  a  iodine 
highly  dilute  solution  of  iodine,  the  latter  will  be  decolorized.  ""cHon. 
The  addition  of  a  little  fresh  starch  paste  makes  this  test  more 
delicate. 

HaSOg  -I-  la  +  HjO  =  HaSO*  +  2HI 

198.  If  sulphurous  anhydride  (SOj)  be  conducted  into  ^.^^^.^^^ 
bromine-water,  it  decolorizes  the  latter,  forming  sulphuric  acid,  gjon  into 
which  may  then  be  detected  by  follov.'ing  §§190,  191.  HaSO,. 

HaSOg  +  Br,  +  HjO  =  H2SO4  -f-  2HBr 
BaClj  +  HjSO,  =  BaSO*  +  2HCI 

Carbonic  Acid  and  Carbonates,  RjCOg. 

199.  Free  carbonic  acid,  HaCOg,  is  only  known  in  solu- 
tion.    Its  solution  has  a  faintly  acid  reaction.     When  warmed,  ^^^ 

it  evolves  carbonic  anhydride,  COa,  a  nearly  odorless,  color-  '  '' 
less  gas,  which  may  be  recognized  by  its  producing  with  lime 
water  a  white  precipitate  of  calcium  carbonate,  CaCOa-  To 
perform  this  test,  the  gas  may  be  passed  into  lime  water;  or  a 
glass  rod,  with  a  drop  of  lime  water  suspended  from  it,  may 
be  held  in  the  test  tube  above  the  surface  of  the  liquid.  It 
should  be  remembered  that  calcium  carbonate  is  soluble  in 
an  excess  of  carbonic  acid  and  that  therefore  the  lime  water 
must  be  present  in  excess.  A  solution  of  barium  hydrate  may 
be  used  with  advantage  instead  of  lime  water,  in  which  case 
there  is  nothing  to  be  feared  from  an  excess  of  carbonic 
anhydride,  since  it  does  not  exert  an  appreciable  solvent  action 
on  barium  carbonate. 


»Thl8  paper  must  be  kept  In  the  dark,  If  kept  at  all.     It  Is  best  fre«h  {v.  §96). 
•  Ferrous  sulphate  Is  formed,  which  produces  TurnbuU's  blue  with  potas- 
sium ferr'cyanlde  (§92). 


I 


3- 


t » 


* 


W. 


-« 


ir  ;■■!•' 


Sri 


RBACTtONS  OF  THE  ACIDS. 


rjaos 


Action  of 
acids  on 
carbon- 
ates. 


SoluWHty 
of  car- 
bonates. 


Bicarbon- 
ates. 


Oxalates. 


Decompo- 
sition of. 


Precipita- 
tion of,  bv 
calcium 

salts. 


Reaction 

with 

HjCrOi. 


200.  All  carbonates  are  decomposed  by  dilute  sulphuric 
(or  hydrochloric  or  nitric)  acid,  carbonic  acid,  H-COg,  being 
set  free.  The  latter  may  then  be  recognized  by  its  charac- 
teristics as  given  in  the  preceding  paragraph,  especially  by  the 
reaction  with  calcium  hydrate. 

201.  The  only  carbonates  which  are  freely  soluble  in 
water  are  potassium  carbonate,  sodium  carbonate  and  ammo- 
nium carbonate.  These  have  an  alkaline  reaction.  A  precip- 
itate is  formed  when  a  soluble  carbonate  is  mixed  with  a  neutral 
solution  of  a  salt  of  any  base^  except  sodiun,  potassium  or 
ammonium. 

202.  The  bicarbonates  or  acid  carbonates  of  sodium  and 
potassium  (NaHCOg,  KKCOg)  may  be  distinguished  from 
the  normal  carbonates  (NajCOg,  KjCOg)  by  the  fact  that  the 
latter  turn  turmeric  paper  brown  while  the  former  do  not 
(§23). 

Oxalic  Acid  and  Oxalates,  RjCjO^. 

203.  Free  oxalic  acid,  HQCjOilf  2H2O,  is  a  white,  crys- 
talline, strongly  acid  solid,  readily  soluble  in  water.  The  free 
acid  and  its  salts  give  no  reaction  with  dilute  sulphuric  acid 
(difference  from  the  carbonate.'),  but,  when  warmed  with 
concentrated  sulphuric  acid,  an  effervescence  takes  place,  due 
to  the  escape  of  CO  and  CO2,  the  oxalic  acid  being  decom- 
posed according  to  the  following  equation : 

HjCjO*  =  HaO  +  CO  +  CO3. 

204*  Solutions  of  an  oxalate  give  with  calcium  salts  a 
precipitate  of  calcium  oxalate,  CaCaO*,  even  in  very  dilute 
neutral  solutions.  This  precipitate  is  colorless,  micro-crystal- 
line, soluble  in  the  mineral  acids,  insoluble  in  acetic  acid  (§46). 
It  is  easily  converted  by  heat  into  calcium  carbonate  and  car- 
bon monoxide. 

205.  Oxalic  acid  or  an  oxalate  when  boiled  with  a 
strongly  acidified  solution  of  potassium  dicTiromate  causes  the 


"Some  ba^eR  which  also  have  acidic  properties  form  exceptions,  such  as 
AsjO|,  etc. 


"'**«»<s'#^^*&fa?- 


.  .t. :,. 


T 


♦^ 


1^ 

f  > 

u 


>S. 


[§20S 


«20yl 


ACIDS  OF  THE  SECOND  GROUP. 


47 


i  by  dilute  sulphuric 
c  acid,  H-COg,  being 
gnized  by  its  charac- 
aph,  especially  by  the 

are  freely  soluble  in 
arbonate  and  ammo- 
;  reaction.  A  precip- 
s  mixed  with  a  neutral 
sodiun,  potassium  or 

bonates  of  sodium  and 
)e  distinguished  from 
,)  by  the  fact  that  the 
le  the  former  do  not 


,  RjCjO*. 

H2O,  is  a  white,  crys- 
le  in  water.  The  free 
th  dilute  sulphuric  acid 
t,  when  warmed  with 
icence  takes  place,  due 
ilic  acid  being  decom- 
ion: 

+  COj. 

e  with  calcium  salts  a 
>4,  even  in  very  dilute 
colorless,  micro-crystal- 
ble  in  acetic  acid  (§46). 
:ium  carbonate  and  car- 

:  when  boiled  with  a 
n  dicTiromate  causes  the 


Lies  form  exceptions,  such  as 


color  to  change  from  red  to  green,  in  consequence  of  a  reduc- 
tion of  chromic  acid  to  a  chromic  salt.    For  example: 
KaCrjOT  +  sHAO*  +  4^3804  = 
KjSOi  +  Cra(S04)s  +  7HaO  +  6CO2 

206.  Soluble  oxalates  give  precipitates  with  most  metallic 
salts,  copper  sulphate,  nickel  sulphate,  manganese  sulphate, 
and  many  others. 

Hydrofluoric  Acid  and  Fluorides,  RF. 

207.  Hydrofluoric  acid  is  an  exceedingly  acid,  volatile, 
corrosive  liquid,  which  etches  glass.     In  order  to  exhibit  this 
property,  warm  a  plate  of  glass  and  rub  a  lump  of  wax  over  HF 
it  so  as  to  give  it  a  thin  and  even  coatmg  of  wax.     After    ^^^^ 
cooling,  write  firmly  on  the  surface  with  a  pencil  or  any  other 
hard  point.    Then  submit  the  surface  to  the  action  of  hydro- 
fluoric acid.    It  will  be  etched  wherever  the  wax  coating  is 
scratched.    Remove  the  wax  by  again  warming  the  plate  and 
wiping  off  the  wax  while  wi  rm.     The  writing  will  now  be 
visible  as  an  etching  on  the  glass. 

208.  If  a  fluoride  is  treated  with  concentrated  sulphuric 

acid,  hydrofluoric  acid  is  set  free  and  may  be  recognized  by  ^^  ^^^ 
its  pungent  odor  and  other  characteristics.  Mix  the  substance  j,^"*,^"'^ 
to  be  tested  (which  should  be  dry)  with  concentrated  sul- 
phuric acid  in  a  shallow  leaden  dish.  Cover  the  dish  imme- 
diately with  a  glass  plate,  prepared  as  described  in  the 
preceding  paragraph,  the  waxed  surface  downward,  and  allow 
the  whole  to  stand  over  night.  If  the  glass  is  etched,  a  fluor- 
ide is  indicated.* 

209.  When  only  a  small  amount  of  substance  is  available, 
it  may  be  advantageously  tested  f^r  fiuorides,  as  follows: 

Pulverize  it  finely  and  dry  it  thoroughly,  if  not  dry  already.  ^^^^^^^ 
Mix  with  twice  its  bulk  of  acid  potassium  sulphate,  KHSO4,  ^^^^  f^,^ 
and  introduce  the  mixture  into  a  clean  and  dry  matrass  (§14)-  fluorides. 
Wipe  out  the  upper  part  of  the  tube  with  filter  paper.     Heat 


iTiiis,  and  ali  othe  experiments  witii  hydrofluoric  acid,  should  be  performed 
under  the  hood,  and  every  precaution  should  be  observed  to  avoid  inhaling  the 
acid  vapour. 


s 

i 

X 


I 


1 4 


'^It 


mm 


W  ■;> 


4fl 


REACTIONS  OF  THE  ACIDS. 


»"2 


the  mixture  to  calm  fusion.  Cut  off  the  tube  at  a  point  just 
above  the  mixture.  Rinse  out  the  upper  part  of  the  tube 
with  distilled  water  and  dry  it.  If  etched,  hydrofluoric  acid  is 
indicated.  If  the  fluoride  tested  be  fluor-spar,  the  reaction  is 
given  by  the  equation : 

CaFa  +  2KHSO4  =  KaSOi  +  CaSO*  +  2HF 

DIVISION   II. 


[&,-■ 


W 


HsPOj. 


PHOSPHATES,  ARSENATES,  CHROMATES,  BORATES  AND 

SILICATES. 

210.  This  division  includes  those  acids  which  are  precip- 
itated by  barium  chloride  in  neutral  but  not  in  acid  solutions 
and  which  evolve  no  gas  when  treated  with  concentrated 
sulphuric  acid. 

The  acids  of  this  section  are  not  readily  volatile. 

Orthophosphoric  Acid  and  Phosphates,  R,HP0«  or  R,P04. 

211.  Free  phosphoric  acid,  HgPOi,  is  a  colorless,  intensely 
sour,  oily  liquid,  which  the  application  of  heat  converts  into 
metaphosphoric  acid,  HPOs,  a  viscous,  semi-solid  mass. 

Free  phosphoric  acid  and  phosphates,  when  mixed  with 
ammonium  chloride,  ammonia  to  alkaline  reaction  and  then 
with  magnesium  chloride  or  sulphate,  give  a  colorless,  crystal- 
line precipitate  (§61),  of  ammonium  magnesium  p!iOsphate, 
MgNHiPOi;  slightly  soluble  in  water;  insoluble  in  strong 
ammonia- water;  readily  soluble  in  dilute  acids.  , 

This  precipitate,  if  filtered  and  washed,  and  then  moistened 
with  silver  nitrate,  turns  canary-yellow,  from  the  formation  of 
silver  phosphate. 
MgNH4P044-3AgN08=  NH4NOS  +  Mg(N08)a  +  AggPO* 

212.  Phosphates,  when  added  to  a  nitric  acid  solution  of 
ammonium  molybdate,  give,  either  at  once  or  on  standing,  a 

twt  yellow,  granular  precipitate  of  ammonium  phospho-molybdate. 

This  is  the  most  sensitive  of  the  reactions  for  the  detection  of 
orthophosphoric  acid.  Arsenic  and  silicic  acids  give  similar 
precipitates  under  similar  conditions. 


Mngnesia 

mixture 

test. 


'■■  ^ii^anSit^ -if fijrtg^jSiia:;* 


!*#■!--«;  Ji.y^^:;^^''"- 


'f-ikCi 


■PNMIi 


ibe  at  a  point  just 
r  part  of  the  tube 
hydrofluoric  acid  is 
spar,  the  reaction  is 

SO4  +  2HF 


;S,  BORATES  AND 

is  which  are  precip- 

lot  in  acid  solutions 

with  concentrated 

volatile. 

•  ■.■-.,■ 

l,HPO«oR  R.PO*. 

a  colorless,  intensely 
>f  heat  converts  into 
!mi-8olid  mass. 
J,  when  mixed  with 
le  reaction  and  then 
e  a  colorless,  crystal- 
agnesium  p!.osphaite, 
insoluble  in  strong 
acids. 

I,  and  then  moistened 
:rom  the  formation  of 

vIg(N08)j  +  AggPO* 
nitric  acid  solution  of 
mce  or  on  standing,  a 
n  phospho-molybdate. 
ns  for  the  detection  of 
icic  acids  give  similar 


»"7] 


ACIDS  OF  THE  SECOND  GROUP. 


49 


FePO« 


213.  Solutions  of  orthophosphates,  when  exactly  neutral- 

ized  with  ammonia  and  treated  with  silver  nitrate,  give  a  phosphate, 
yellow  precipitate  of  silver  phosphate,  AggPO*,  which  is  easily 
decomposed  by  dilute  acidd  or  alkalies. 

214.  A  neutral   solution  of    an  urthophosphate,   when 
treated  with  neutral  solutions  of  ferric  or  aluminium  salts,  gives 
a  white  precipitate   (§100)   of  ferric  phosphate,  FePO^,  or  '^^'^ 
aluminium  phosphate,  AIPO4;   insoluble  in  acetic  acid,  but  AIPO4. 
soluble  in  the  mineral  acids. 

If  either  of  these  precipitates  be  dried  at  a  high  temperature 
and  then  mixed  with  a  little  powdered  metallic  magnesium 
and  strongly  ignited  in  a  matrass,  magnesium  phosphide  will 
be  formed,  MgaPj. 

2FeP04  +  iiMg  =  2Fe  +  8MgO  +  Mga  P2 

If  the  residue  be  then  moistened  with  a  drop  of  hydrochlo- 
ric acid,  phosphine,  PHg,  will  be  evolved  and  may  be  detected 
by  its  peculiar  odor  and  by  its  property  of  emitting  light  in  a 
darkened  room. 

Arsenic  Acid  and  Arsenates,  RjHAsOi  or  RSA8O4. 

215.  Free  arsenic  acid  closely  resembles  free  phosphoric  Free 
acid,  and  its  salts  give  reactions  similar  to  those  described  in  H8A804. 
S8211-212.    The  precipitate  of  magnesium  ammonium  arsen- 
ate, MgNHiAsO*,  is  indistinguishable   in    appearance    from 
magnesium  ammonium  phosphate,  but  may  be  distinguished 

from  the  latter  by  giving  a  red  instead  of  a  yellow  coloration 
on  treatment  with  silver  nitrate. 

MgNH4As04  +  sAgNOa  = 
Ag8As04  +  NH4NO8  +  Mg(N08)2 

216.  Solutions  of  an  arsenate,  when  exactly  neutralized 

with  ammonia  and  treated  with  silver  nitrate,  give  a  brick-red  AgjAsOi. 
precipitate  of  silver  arsenate,  Ag3As04,  soluble  in  dilute  acids 
or  alkalies.      Silver  arsenate  is  much  less  soluble  in  acetic 
acid  than  silver  phosphate. 

217.  An  arsenate,  on  gently  warming  with  a  large 
excess  of  concentrated  hydrochloric  acid  and  tin  foil,  will  give 
a  brownish  precipitate  of  finely  divided  arsenic.  (Distinction 
from  all  other  acids  of  this  group). 


t 


"1  ,'■_ 


II 


;  4 


fa 


» i 


K^  I 


\t\ 


>  f  , 


WW  ' 


80 


CrO,. 


AvjCrOi. 


hftCrO,. 


BaCi04. 


ReduC' 
tion  of 
CrO,. 


H|BO, 


Flame 
test. 


M». 


RBACTIONS  OF  THE  ACIDS. 


t»"5 


2 1 8.  Other  tests  for  arsenic  acid  are  given  under  the 
head  of  arsenic,  §§166-173. 

Chromic  Acid  and  Chromatrb,  R,CrO«. 

219*  Chromic  acid,  H2Cr04,  is  not  known  in  the  free 
state,  since  it  separates  readily  into  HjO  and  CrOg  (chromic 
anhydride).  The  latter  is  a  ruby-red,  crystalline  solid,  readily 
soluble  in  water,  to  which  it  gives  a  reddish  or  yellowish 
coloration,  even  in  highly  dilute  solutions.  The  soluble  chro- 
mates  giv«»  in  nei  .ral  solutions  with  nitrate  of  sliver  a  red 
pirecipilatc  of  silver  chronr.ate,  AgjCr04,  soluble  in  ammonia 
and  in  mineral  acids,  nearly  insoluble  in  acetic  acid. 

220.  Mercurous  nitrate  gives  a  very  similar  reaction,  pre- 
cipitating the  chromic  acid  as  mercurous  chromate,  Hj>*3Cr04, 
blood-red. 

221.  Neutral  solutions  of  chromates  give,  with  barium 
chlo'.  Ide  or  nitrate,  a  yeliow,  and  with  lead  nitrate  or  acetate, 
an  orange-yellow  precipitate,  respectively  BaCiO«  (§55 )»  and 
PbCrO^  (§134).  Both  these  precipitates,  especially  the  latter, 
are  nearly  insoluble  in  dilute  acetic  acid  but  are  somewhat 
soluble  in  dilute  mineral  acids. 

222.  If  a  dilute  solution  of  chromic  acid,  or  of  a  chi'omate 
be  acidified,  treated  with  a  few  drops  of  alcohol  and  warmed, 
the  color  of  the  solution  will  change  from  red  to  green.  Sul- 
phurous acid,  hydrogen  sulphide  and  many  other  reducing 
agents  will  effect  the  same  change. 

2H,Cr04  +  3Hi,S0«  =  Cra(S04)8  +  SHjO 
BcRic  Acid  ano  Borates. 

223.  Boric  acid,  HgBOg,  is  thrown  down  as  a  white, 
crystalline  precipitate  on  the  addition  of  a  strong  acid  to  a 
concentrated  solution  of  a  borate.  ,  '  >?; . 

224.  Free  boric  ?.cid,  but  no'  the  borates.  wiL  vmynri  a 
lively  grec'n  coloration  to  the  Bunseii  flame.  Borates,  when 
moistened  with  sulphuric  acid  and  introduced  into  the  flame, 
give  the  i>nme  coloration  which,  however,  is  often  masked  by 
the  presence  of  sodiun;  or  some  other  flame-coHring  base. 

22ij.  Alcohol,  if  boiled  with  free  boric  acid  or  with  a 
•nix^ure  of  sulphuric  acij  and  a  borate,  gives  off  vapours, 


"  ■•ii'  &,:^.'j^:>i^-  ^M^i'M^ 


-i  'J.'.:'.*;->,;'.v*i».^:-^:<  .">...d 


^mm^~ 


T 


[|"S 
re  given  under  the 

known  in  the  free 
and  CrO,  (chromic 
stalline  solid,  readily 
eddish  or  yellowish 
,  The  soluble  chro- 
rate  of  sliver  a  red 
soluble  in  ammonia 
cetic  acid. 

similar  reaction,  pre- 
chromate,  Hif2Cr04, 

s  give,  with  barium 
ad  nitrate  or  acetate, 
f  BaCrO*  (§55).  and 
,  especially  the  latter, 
i   but  are  somewhat 

icid,  or  of  a  chromate 

alcohol  and  warmed, 

n  red  to  green.     Sul- 

many  other  reducing 

)4)8+5H20        ^ 

[S. 

vn  down  as  a  wliite, 
3f  a  strong  acid  to  a 

borates,  wib  imvnrt  a 
lame.  Borates,  when 
iduced  into  the  flame, 
;r,  is  often  masked  by 
lame-coloring  base, 
boric  acid  or  with  a 
ite,  gives  off  vapours, 


§3J9] 


ACIDS  OF  THE  SECOND  GROUP. 


51 


which,  when  ignited,  burn  v,  th  a  green  flame.     No  other  ^icohoi 
substances  will  interfere  with  t'  «8  test,  which  is  most  advanta-  test  (or 
geously  executed  as  follows.     Provide  a  test-tube  with  a  H,BO,. 
closely  fitting  cork  bearing  a  straight  piece  of  glass  tubing 
about  two  inches  long.    Introduce  into  the  tube  about  3  c.c. 
of  alcohol, >   I  c.c.  concentrated  sulphuric  acid,  and  not  too 
small  a  quantity  of  the  substance  to  be  tested. 

Warm  the  contents  of  the  test  tube  gradually  to  boiling  and 
ignite  the  vapor  as  it  issues  from  the  delivery  tube.  The 
margin  of  the  flame  will  appear  green  in  the  presence  even 
of  a  very  small  amount  of  a  borate. 

226.  If  turmeric  paper  be  immersed  in  a  solution  of  a  Turmeric 
borate  which  has  previously  been  acidified  with  hydrochloric  paper 
acid,  the  paper  will  turn  red,  either  at  once  or  upon  drying.  **"'" 
The  reddened  turmeric  blackens  on  treatment  with  ammonia. 

227.  In  neutral  and  somewhat  concentrated  solutions  of 

borates,  barium  chloride  will  produce  a  precipitate  of  varying 

composition.     This  test  is  neither  sensitive  nor  characteristic. 

Accordingly  boric  acid  may  often  be  detected  by  the  test  of 

§225  in  solutions  which    give  no  precipitate   with  barium 

chloride.     , 

Silicic  Acin  and  Silicates. 

SiO)|. 

228.  Free  silicic  acid,  HjSiOs,  has  no  acid  reaction  and 

appears  in,  at  least,  three  distinct  forms :  a,  soluble  in  water, 
*,  gelatinous,  c,  insoluble  in  water,  pulverulent.  The  forms 
a  and  b  are  converted  into  the  insoluble  form,  c,  if  the  solution 
containing  them  is  evaporated  to  dryness. 

A  solution  of  any  silicate,  if  it  be  acidified  with  hydrochloric 
acid,  evaporated  to  dryness,  and  then  treated  with  dilute 
hydrochloric  acid,  will  leave  an  insoluble  residue  of  silicic 
acid  The  solution  will  contain  the  bases  (as  chlorides)  and 
any  other  acids  that  were  present. 

229.  The  only  soluble  silicates  are  tho?e  of  sodium  and  insolu- 
potassium.     A  solution  of  either  of  these  may  be  precipitated  biiity  o£ 
by  a  salt  of  any  other  base. 


Separation 
of  SiOji. 


gillcatei. 


'Methvl  alcohol  or  wood  tpirit  is  preferable  to  common  alcohol  for  the 
purposes  of  this  tent. 


5.    , 

I 'A 


»^. 


.>>-«VK«-.'«<lMI«tW?'<<«>MK«i<>l<ffiE^^ 


$» 


REACTIONS  OF  THE  ACIDS. 


[§^34 


PuRlon  of 
dlllcates. 


230.  Many  silicates  are  incapable  of  being  dissolved  or 
decomposed  by  sulphuric  or  other  strong  acids.  Such  silicates 
may  be  fused  with  four  times  their  weight  of  sodium  carbonate 
and  a  little  sodium  nitrate.  The  product  resulting  from  this 
fusion  can  be  decomposed  by  boiling  with  dilute  hydrochloric 
acid  and  water,  and  the  silicic  acid  separated  as  in  4^228.  The 
resulting  solution  can  be  .used  for  the  detection  of  other  acids. 

23 1  •  Silicic  acid  is  soluble  in  aqueous  hydrofluoric  acid, 
forming  fluosilicic  acid,  HjSiFe.  If  the  latter  is  warmed  with 
concentrated  sulphuric  acid,  the  whole  of  the  silicon  escapes  in 

0*810  °"  ^^^  ^°^^  °^  ^^'^  5^*  ^'^*"  ®>'  ^"'^•^c''  heating,  the  excess  of 
hydrofluoric  acid  may  also  be  expelled.  In  this  way  the  silica 
may  be  removed  from  any  silicate,  the  bases  being  at  the  same 
time  obtained  as  sulphates. 

332.  If  silica  or  a  silicate  is  fused  with  a  bead  of  "  micro- 
Metaphos- cosmic  Salt"  (v.  §ii)  in  the  oxidizing  flame,  the  silica  will 
p  ate  ea  remain  floating  as  a  cloud  in  the  bead,  and   will  render  it 

opaque  or  opalescent  when  cold.     Small  quantities  of  silica 
can  not  always  be  detected  by  this  test. 

333.  Silicic  acid,  HjSiOs,  or  silicic  anhydride,  SiOj,  into 
which  the  former  is  converted  by  ignition,  dissolves  in  the 
sodium  carbonate  bead,  forming  a  clear  glass  of  sodium 
silicate,  NajSiOg. 

If  this  bead  be  dissolved  in  dilute  hydrochloric  acid,  the 
solution  will  gelatinize,  either  at  once  or  on  evaporation. 
SiOj  +  NajCOg  =  NaaSiOs  +  CO, 
NajSiOg  +  2HCI  =  2NaCl  +  H2Si08 


GROUP  III. 

Thiv  group  includes  those  acids  which  are  precipitated  by 
silver  nitrate  in  a  solution  acidified  by  dilute  nitric  acid. 

DIVISION  I. 

SULPHOCYANATES,  FERROCYANIDES  AND 
FERRICYANIDES. 

234.     This  division  comprises  those  acids  which  give  a  red 
or  blue  coloration  with  iron  salts. 


'-^^mmiii^ti  '■■auim^^''-  ■ 


/wiiiSSi?i 


T 


*» 


[§'34 

:  being  dissolved  or 
acids.    Such  silicates 
of  sodium  carbonate 
t  resulting  from  this 
h  dilute  hydrochloric 
ted  as  in  ^228.    The 
;ction  of  other  acids. 
)U8  hydrofluoric  acid, 
atter  is  warmed  with 
the  silicon  escapes  in 
leating,  the  excess  of 
In  this  way  the  silica 
ises  being  at  the  same 

th  a  bead  of  "  micro- 
flame,  the  silica  will 
d,  and  will  render  it 
ill  quantities  of  silica 

anhydride,  SiOj,  into 
tion,  dissolves  in  the 
car   glass   of   sodium 

lydrochlotlc  acid,  the 
on  evaporation. 

8  +  CO, 

+  HjSiOa  • 


;h  are  precipitated  by 
ilute  nitric  acid. 


AN  IDES  AND 


acids  which  give  a  red 


§'40] 


AC/DS  OF  THB  THIRD  GROUP. 


53 


Ferric 


SULPHOCYANIC  AciD  AND  SULPHOCYANATEH,  RSCN. 

335.  Sulphocyanic  acid  is,  in  the  free  state,  an  oily,  sour 
liquid,  which  readily  decomposes.     It  forms  with  the  alkalies 

and  alkaline  earths  colorless  salts,  which,  when  mixed  with  a ^ 

ferric  salt,  give  rise  to  an  intense  blood-red  coloration,  due  to  »uipho- 
the  formation  of  a  double  ferric  sulphocyanate.     For  example:  cvnnnte. 
FeCl,  +  12KSCN  =  3KCI  +  Fe(SCN)8(KSCN)9 

If  this  red  solution  be  shaken  with  ether,  the  ethereal  layer 
will  -xcquire  a  deep  red  color.  This  reaction  is  very  sensitive 
and  is  peculiar  to  sulphocyanates. 

216.     If  a  soluble  sulphocyanate  be  treated  with  sulphurous 

...  .  •    -J.   ^        t  Cuprouf 

acid  and  copper  sulphate,  a  white,  amorphous  precipitate  of  g^iphj,. 
Cua(SCN)a,  insoluble  in  dilute  acids,  will  appear.  emanate. 

2CUSO4  +  sKSCN  -f-  HjSOb  +  HjO  = 
Cuj(SCN)j  +  4K1SO4  -f  2H3SO4 

HYD.IOFKRROCYAN  n  AciD  AND  Fbrrocyanidks,  R4Fe(CN)». 

237.  Free  hydroferrocyanic  acid,  H4Fe(CN)6,  appears  as 
a  crystalline  precipitate,  consisting  of  colorless,  pearly'  scales, 
difficultly  soluble  in  water,  when  hydrochloric  acid  is  added  to 
a  concentrated  solution  of  a  ferrocyanide.  The  free  acid 
readily  decomposes,  turning  blue  at  the  same  time. 

238.  The  soluble  ferrocyanides  possess  a  pale  yellow 
color.  They  give  with  ferrous  salts  a  colorless  precipitate, 
which  rapidly  turns  blue,  with  ferric  salts  a  deep  blue  colora- 
tion or  precipitate  of  Prussian  blue.  The  composition  of  these 
precipitates  varies  with  the  conditions  of  the  experiment. 

239.  Soluble  ferrocyanides  produce  with  copper  salts, 
even  in  highly  dilute  solutions,  a  red  precipitate,  insoluble  in 

the  cold,  in  all  acids.     This  precipitate  has  the  composition^^    ^^^^^ 
Cu2Fe(CN)6,  when  formed  in  the  presence  of  an  excess  of^ocyanide. 
copper  salt.     If  the  ferrocyanide  is  in  excess,  the  precipitate 
has  the  composition  Cu3R2(Fe(CN)6)2. 

2CUSO4  +  K4Fe(CN)6  =  Cu2Fe(CN)6  +  2K2SO4 
3CUSO4  +  2K4Fe(CN)e  =  CU3K2  (Fe(CN)6)2  +  3K2SO4 

Hydroferricyanic  Acid  and  Fkrricyanides,  RsKe  (CN)^. 

240.  Free  hydroferricyanic  acid  is  a  soluble,  reddish  brown, 
crystalline  substance.     The  soluble  ferricyanides  are  red  salts. 


.,ji-. -.i.r.is.',i}^iiMBjwwi«p««-»,«vi,(^,rf^.*9tj^rtae.  "Sfi 


"C 


'i 


I 


I 


^ 


I 


\^'. 


A 


.It 


i  ;-' 


«■'■■ . 


♦«k 


RRACT/ONS  OF  THE  ACfDS. 


ri344 


the  solutions  of  which  are  reddish  yellow,  even  when  highly 

dilute.     With  ferrous  salts,  they  /|pve  a  deep  blue  precipitate 

of  Tumbull's  blue,  Fe8(CN)„.     With  ferric  salts  the  ferricy- 

anides  give  a  deep  reddish  brown  coloration  but  no  precipitate. 

341.     If  a  soluble  ferricyanide  is  slightly  acidified   with 

Oxldliing  hydrochloric  acid  and  treated  with  zinc  sulphate'  and  potas- 

nction  of   slum  iodide,  the  solution  will  turn  brown,  from  the  separation 

ierricjr»n.  q{  iodine,  and,  if  the  solution  be  then  shaken  with  chloroform, 

the  latter  will  turn  violet;  see  §258. 

K,Fe(CN).  H-  KI  =  K4Fe(CN),  +  I 

DIVISION  II. 
NITRITES,   HYPOCHLORITES   AND   CHLORITES. 

This  division  comprises  those  acids  which  bleach  indigo 
solution. 

Nitrous  Acid  and  Nitrites,  RNO,. 

242.  Free  nitrous  acid,  HNOj,  8p>ontaneou8ly  decomposes 
I  ubiiit  ^^^^  water  and  NjOn,  and  the  latter  into  NO  and  NO2,  exhib- 
olnitrou*  iting  the  brown  fumes  or  coloration  of  the  latter.  Nitrous 
ucid.         acid  is  set  free  from  soluble  nitrites  when  the  latter  are  treated 

with  hydrochloric  or  dilute  sulphuric  acid. 

HjSO,  -f  2NaNOa  =  Na^O*  +  aHNO,  = 
NajS04  +  HaO  +  NO  +  NO, 

243.  If  a  solution  of  a  nitrite  be  colored  blue  with  a  drop 
of  indigo  solution,  then  acidified  with  acetic  or  hydrochloric 
acid  and  boiled,  the  blue  color  of  the  indigo  will  be  destroyed. 

Nitrates  when  treated  with  acetic  acid  and  indigo  solution 
do  not  destroy  the  color  of  the  latter.  This  test  may  there- 
fore be  used  to  distinguished  nitrites  from  nitrates. 

244.  A  solution  of  a  nitrite  if  treated  with  potassium 
iodide  and  then  acidified,  sets  iodine  free,  and  the  latter  may 

Iodine  test.  ^^  detected   by  the  blue  color  which  it  gives  with  starch 

paste  (§259)- 
2NaNOa-|-2KI-|-4HCl=2KCl+2NaCl+NjOa-|-2HaO+Ia 

>The  addition  of  the  zinc  sulpliate,  as  recomm'^nded,  greatly  enhances  the 
sensitiveness  of  this  reaction. 


ii^Jll 


'■»".  Kh£  «»;6^?jiS.>>iSi«fo',>*.*3*l|fe^' 


::*s- 


m}*^*^i^&- 


T 


S.  fl'44 

,  even  when  highly 
leep  blue  precipitate 
•ric  salts  the  ferricy- 
m  but  no  precipitate, 
ghtly  acidified  with 
sulphate*  and  potas- 
from  the  separation 
cen  with  chloroform, 

:n),  +  I 

^  CHLORITES. 
which  bleach  indigo 

,  RNOj. 

taneously  decomposes 
NO  and  NO,,  exhib- 
;  the  latter.  Nitrous 
1  the  latter  are  treated 
d. 

+  2HNOa  = 
f  NOj 

ored  blue  with  a  drop 
acetic  or  hydrochloric 
iigo  will  be  destroyed, 
cid  and  indigo  solution 
This  test  may  there- 
>m  nitrates. 

reated  with  potassium 
ee,  and  the  latter  may 
I  it  gives  with  starch 

Cl+NaOa+aHjO-Hla 


»»S>1 


FRRB  HALOIDS. 


55 


»>«nded,  greatly  enhances  the 


245.  The  most  delicate  reaction  for  nitrites,  known  as 
Zambelli's  test,  may  be  executed  as  follows.  Add  to  the 
solution  sulphanilic  acid,  NHaC8H4SO|H,  nnd  acidify  with 
dilute  sulphuric  acid.     After  standing  a  few  minutes,  add  a 

drop  of  a  saturated  solution  of  phenol,  CgHsOH,  then  render  rcoction. 
the  solution  alkaline  with  sodium  hydrate.     A  yellow  colora- 
tion indicates  a  nitrite.     This  extraordinarily  sensitive  reaction 
is  more  particularly  adopted  to  the  detection  of  nitrites  in 
drinking  water  (§374). 

HvpociiLORoui  Acid  and  Hypochlohitm,  RCIO. 

246.  Free  hypochlorous  acid  has  the  peculiar  and  dis-  ^  ,^,^  ^ 
7         ,         .    .  .     .  .       ,  ,.  T      1  JM     Addlfled 

tinctive  odor  of  chloride  of  hme.     It  decomposes  very  readily  hypochio- 

into  hydrochloric  acid,  oxygen,  and  other  products.     Either  ritei  liber- 
the  free  acid  or  its  salts,  if  mixed  with  a  highly  dilute  indigo  ■'« chlorine, 
solution,  rapidly  bleach  the  latter. 

247.  A  hypochlorite  on  treatment  with  hydrochloric  acid 
evolves  chlorine  (§§252-254). 

2NaOCl  -f-  2HCI  =  2NaCl  +  HjO  -f  CI, 

248.  A  hypochlorite  when  mixed  with  a  drop  of  potas- 
sium iodide  and  acidified  with  hydrochloric  acid  sets  iodine  free. 

Chlorous  Acid  and  Chloritbs,  RCIO9. 

249.  Free  chlorous  acid  is  a  very  unstable  compound 
resembling  hypochlorous  acid.  Like  the  latter,  it  will  bleach 
indigo  solution.  Chlorites,  unlike  the  hypochlorites,  will  not 
bleach  neutral  or  alkaline  indigo  solution,  but  will  do  so  if 
acidified  with  hydrochloric  or  sulphuric  acid. 

250.  Chlorites  give  reactions  similar  to  those  of  the 
hypochlorites  mentioned  in  §§247-248. 

Free  Haloids,  Clj,  Br,,  Ij. 

251 .  The  free  huloids,  chlorine,  bromine  and  iodine,  may 
be  properly  considered  here,  since,  although  not  acids,  they 
form  a  precipitate  with  silver  nitrate  in  neutral  or  acid  solu- 
tions and  bleach  indigo. 

252.  Free  chlorine  is  a  yellow  gas,  which  dissolves  in 
water  to  form  a  yellow  solution  possessing  the  suffocating 


'I  M 


.vM«aM»»iiif»«e»K»v»«B»«i>»iuu-««%aijsiT.>i»*M«iEt^^^ 


5<5 


REACTIONS  OF  THE  ACIDS. 


(§*S8 


Reactions 
of  free 
chlorine. 


Reactions 
of  free 
bromine. 


Detection 
of  free 
iodine. 


odor  of  the  gas.  Chlorine-water,  when  treated  with  ammo- 
nia, causes  an  efferveficence  of  nitrogen  and  simultaneous 
formation  of  ammoniuni  chloride. 

3CI2  +  SNHg  =  Na  =  6NH4CI 
253*     ^^  potassium  bromide  be  added  in  excess  to  chlorine- 
water  and  the  whole  shaken  with  chloroform,  the  latter  will 
turn  brown  (§255). 

KBr  +  CI  =  KCl  +  Br 
If  treated  in  a  similar  way  with  an  excess  of  potassium 
iodide  and  chloroform,  the  latter  will  turn  violet  (§258). 
KI  +  CI  =   KCl  +  I 

254-  If  a  few  drops  of  chloroform  be  colored  faintly  violet 
by  the  audition  of  a  minute  trace  of  iodine,  and  if  it  then  be 
shaken  with  an  excess  of  chlorine-water,  the  violet  color  will 
disappear  in  consequence  of  the  formation  of  iodine  tri- 
chloride. 

I2  +  3CI2  =  2ICI8 

255-  Free  bromine  dissolves  in  water  to  the  extent  of 
about  three  per  cent.,  forming  a  reddish  brown  liquid,  which 
smells  of  bromine,  and  which  sets  nitrogen  free  from  ammonia. 

3 Bra  -h  SNHg  =  N2  +  6NH4Br 

Bromine-water,  if  shaken  with  a  few  drops  of  chloroform 
or  carbou  disulphide,  imparts  to  the  latter  a  yello\''ish  brown 
color,  in  consequence  of  a  tendency  w'lich  bromine  exhibits,  to 
leave  the  water,  in  v.rhich  it  is  but  slightly  soluble,  and  to 
dissolve  in  the  chk  roform  or  carbon  disulphide,  in  which  it  is 
rrtely  soluble. 

256.  Bromine- water  when  shaken  with  raw  starch,  colors 
the  latter  yellow. 

257-  Bromine  if  treated  with  potassium  iodide  in  excess, 
liberates  iodine.  " 

2  5S.  Iodine  is  but  very  slightly  soluble  in  water,  the  solu- 
tion b^lng  of  a  pale  straw-color.  It  is  much  more  freely  soluble 
in  a  solution  of  p^  tassium  iodide  in  water.  If  either  of  these 
solutions  is  shaken  with  chloroform,  the  latter  becomes  violet.  1. 


v;^' 


'Tlie  violet  color  is  not  due  to  a  compound  of  iodine,  since  no  ciiemical 
reaction  occurs,  but  merel  v  to  a  solution  of  iodine  in  cliloroform. 


'''^fSxik!J^m^^:sh^mi-^-<^^l^^k^  <^'^~'^  '"^ 


^PU5^    ,  iii. 


T^'  smrr 


%.«. 


s. 


(§258 


1  treated  with  ammo- 
en   and  simultaneous 

NH4CI 

i  in  excess  to  chlorine- 
reform,  the  latter  will 

\-  Br 

i  excess  of  potassium 

rn  violet  (§258). 

f  I 

36  colored  faintly  violet 
»dine,  and  if  it  then  be 
:r,  the  violet  color  will 
•mation  of  iodine    tri- 

■^1 
'ig 

vater  to  the  extent  of 

jh  brown  liquid,  which 

yen  free  from  ammonia. 

6NH4Br 

w  drops  of  chloroform 

itter  a  yellowish  brown 

lich  bromine  exhibits,  to 

slightly  soluble,  and  to 

lisuiphide,  in  which  it  is 

n  with  raw  starch,  colors 

tassium  iodide  in  excess, 

>luble  in  water,  the  solu- 
Buch  more  freely  soluble 
vater.  If  either  of  these 
e  latter  becomes  violet.  1. 


mmfmm>v^'9'm''f^'f*''*i*'^'^'y'''''^*^i''**yilff''f^- 


1  of  iodine,  since  no  clieinical 
ine  in  chloroform. 


§264] 


AC  IDS  OF  THE  THIRD  GROUP. 


S7 


By  repeatedly  shaking  with  fresh  portions  of  chloroform  the 
whole  of  the  free  iodme  n^ay  be  removed. 

259.  If  to  a  dilute  starch  paste,  prepared  by  boiling  one 
gram  of  starch  with  100  c.c.  water  for  five  minutes,  be  added  gjjj^ch 
a  dilute  iodine  solution,  the  starch  paste  will  acquire  a  beauti-  paste 
£ul  blue  color.     This  is  the  most  sensitive  and  characteristic  reaction, 
reaction  for  free  iodine.     The  reaction  does  not  take  place  in 

hot  solutions.  The  stai  ch  paste  should  be  used  fresh.  It  may 
however  be  preserved  for  some  weeks  by  keeping  it  in  a 
tightly  stoppered  bottle  containing  a  drop  of  chloroform. 

DIVISION   III. 
SULPHIDES,   POLYSULPHIDES   AN"  TKIOSULPHATES. 

260.  This  division  comprises  those  acids  which  give  a 
black  precipitate  with  acid  solutions  of  silver  nitrate. 

,     Sulphides,  RjS,  and  Polysulphides,  RjSi. 

261.  Hydrogen  sulphide  is  a  colorless  gas,  having  a 
characteristic  odor,  which  gives  a  black  precipitate  with  alka- 
line, neutral  or  acid  solutions  of  silver  or  lead. 

A  test  paper,  prepar^id  by  soaking  white  paper  in  a  solution 
of   nitrate   of  lead  and  then    drying  it,   offers  a  convenient  Lead  paper 
rtieans  of  detecting  this  compound.     A  strip  of  it  is  rapidly  **,"  J*,*' *°'" 
browned  or  blackened,  when  brought  into  contact  with  hydro- 
gen sulphide. 

A  solution  containing  sufficient  free  iodine  to  be  of  a  straw- 
coior  is  instantly  decolorized  by  hydrogen  sulphide. 
HaS  +  I2  =  2HI  +  S 

262.  A  soluble,  normal,  metallic  sulphide,  R2S,  if  acidified 
with  dilute  sulphuric  acid,  evolves  hydrogen  sulphide  (which 
rr.ay  be  recognized  as  above ">  without  separation  of  sulphur. 

K2S  -,-  H2SO4  =  K2SO4  +  H3S 

263.  A  soluble,  normal,  metallic  sulphide,  if  moistened  and 
placed  in  contact  with  a  clean  piece  of  metallic  silver,  produces 
a  black  stain  upon  the  latter. 

NajS  +  Ag2  +  O  +  H^O  =  Ag^S  +  2NaOH 

264.  A  soluble,  metallic  polysulphide  (usually  yellow), 
when  acidified  with  dilute  hydrochloric  or  sulphuric  acid, 
evolves  hydrogen   sulphide,  free   sulphur  appearing  at  the 


sulpliides. 


Polysul- 
pliides. 


.    >#. 


58 


REACTIONS  OF  THE  ACIDS. 


Wio 


8 1'ii) ,..- v.! 


same  time  as  a  white  precipitate.  This  separation  nf  free 
sulphi  i'  distinguishes  the  polysulphides  from  the  noriaal  sul- 
phides. 

HaS,  +  2HCI  =  2KCI  +  HjS  +  S._. 

Thiosulphates,  RjSjOt. 

265.  Free  thiosulphuric  acid,  H3S2O3,  rapidly  decom- 
poses, when  in  concentrated  solution,  into  sulphurous  acid, 
H2SO8,  and  free  sulphur,  ^ich  of  which  may  be  recognized  by 
the  aopropriate  tests  (§196,  198).  Highly  dilute  solutions 
decompose  in  the  same  way  but  much  more  slowly. 

266.  If  a  dilute  solution  of  a  thiosulphate  is  acidified,  thio- 
sulphuric acid  is  set  free.  The  latter  then  decomposes  as 
given  above,  the  solution  slowly  turning  nulky  from  the  sepa- 
ration of  free  sulphur. 

267.  A  solution  of  a  thiosulphate,  R2S2O8,  gives  with  silver 

nitrate  a  whitish   yellow   precipitate   of   silver   thiosulphate. 
Reaction       .       „  ^         m    •  ,    •      •        1    i  ,      •        ft  •  ,       u 

ofthiosul-   Ag2S208.     This  compound  is  insoluble  m  dilute  acids,   but 

phates  with  soluble  in  a  solution  of  a  thiosulphate.     It  decomposes  readily 

•''^^''         and  on  boiling  turns  black,  from  the  formation  of  silver  sul- 
nitrate.  ,  .  , 

phide. 

AgaSjOa  +  H2O  =  AgaS  +  Hj  SO4 

268.  A  solution  of  a  thiosulphate  instantly  decolorizes  an 
iodine  solution. 

2Na2S208  +  2I  =  NaaS406  +  2NaI  <  ,• 

DIVISION  IV.      '  '  ': 

CHLORIDES,  BROMIDES,  IODIDES  AND  CYANIDES. 

269.  This  division  comprises  those  acids'  which  do  not 
exhibit  the  reactions  of  Divisions  I,  II  and  III. 

Hydrochloric  Acid  and  Chlorides,  RCI. 

270.  Free  hydrochloric  acid  dissolves  in  water,  forming  a 
strongly  acid  soln^^on.  The  free  acid  and  its  salts  give  with 
silver  nitrate  in  iisjutral  or  acid  solutions  a  curdy,  white  pre- 
cipitate of  silver  chloride,  AgjCla,  {v.  note  p.  27),  which 
becomes  violet  on  exposure  to  the  light,  especially  in  the 
presence  of  silver  nitrate.  The  separation  of  this  precipitate 
is  greatly  facilitated  by  violent  shaking. 


Test  for 
chlorides 
with 
AgNOj. 


}  separation  nf  free 
rom  the  noriaal  sul- 

2S   +    Sx_t 


jOa,  rapidly  decom- 
nto  sulphurous  acid, 
lay  be  recognized  by 
ghly  dilute  solutions 
ore  slowly, 
hate  is  acidified,  thio- 
then  decomposes  as 
nulky  from  ihe  sepa- 

SaOa,  gives  with  silver 
t  silver  thiosulphate, 
in  dilute  acids,  but 
It  decomposes  readily 
rmation  of  silver  sul- 

h  Ha  SO4 

istantly  decolorizes  an 

(  +  2Nal         -  >;/ 


AND  CYANIDES. 

J  acidsr  which  do  not 
id  III. 

)RIDBS,  RCl. 

res  in  water,  forming  a 
ind  its  salts  give  with 
)ns  a  curdy,  white  pre- 
V.  note  p.  27),  which 
ight,  especially  in  the 
tion  of  this  precipitate 


§^76] 


AC/DS  OF  THE  THIRD  GROUP 


59 


Silver  chloride  dissolves  readily  in  ammonia  or  in  a  solution  Silver 
of  sodium  thiosulphate.     It  is  nearly  insoluble  in  nitric  acid. 

271.  If  hydrochloric  acid  or  a  soluble  chloride  is  treated 
with  manganese  dioxide  and  warmed  with  concentrated  sul- 
phuric acid,  cLlorine      liberated.     (Cf.  §§252-254.) 

272.  If  a  solcb.o  chloride  is  warmed  with  a  mixture  of 
potassium  dichromate  and  concentrated  sulphuric  acid,  chromyl  ^']*^J"^' 
chloride,  CrOaClj,  is  formed.     The  latter  is  a  volatile,  red  *^ 
liquid,  which,  on  warming,  passes  off  as  a  red  vapour.     If  the 
operation  is  performed  in  a  tubulated  test-tube,  the  vapour 

may  be  passed  into  ammonia  to  which  it  imparts  a  canary- 
yellow  coloring  owing  to  the  formation  of  ammonium  chro- 
mate.    .,..■.  -  -"-.■■:.--:;  ■ 

KjCraO;  +  H2SO4  +  4HCI  =  KjSO*  +  2Cr02Cl3  +  3H2O 

CrOjClj  +  4NH8  +  2HaO  =  (NH4)2Cr04  +  2NH4CI 

Hydrodrciic  Acid  and  Bromides,  RBr. 

273.  Hydrobromic  acid,  HBr,  gradually  turns  brown 
when  exposed  to  the  air,  in  consequence  of  partial  oxidation. 

2  HBr  +  O  =  H2O  +  Br2 
The  free  acid  or  soluble  bromides  give  with  nitrate  of  silver  silver 
in  neutral  or  acid  solutions  a  curdy,  yellowish  precipitate  of  »"•'>•"'<»«. 
silver  bromide.     This  is  difficultly  soluble  in  dilute  ammonia; 
soluble  in  sodium  thiosulphate;  insoluble  in  acids. 

274.  Free  hydrobromic  acid  or  a  soluble  bromide,  when 
treated  cautiously  with  chlorine- water,  drop  by  drop,  turns 
brown,  from  the  separation  of  free  bromine. 

HBi:+  Cl=  HCl  +  Br 
If  the  solution  be  then  shaken  with  chloroform  or  carbon 
disulphide,  this  will  be  colored  brown  by  the  bromine. 

275.  Hydrobromic  acid  or  soluble  bromides,  if  warmed 
with  concentrated  sulphuric  acid,  or,  better,  with  a  mixture  of 
sulphuric  acid  and  manganese  dioxide,  evolve  brown  vapours 
of  bromine. 

Hydriodic  Acid  and  Iodides,  RI. 

276.  Solutions  of  free  hydriodic  acid  rapidly  turn  brown 
in  contact  with  the  air,  in  consequence  of  oxidation.        < 


"  1 
'1 


J 


^.. 


l\  ff 


i>. 


%^^ 


4^ 


ft' 


«0 


Silver 
iodide. 


Reaction 
of  I  witii 
starcli. 


Ferric 
salts  with 
iodides. 


Reaction 
with  con- 
centrated 
HjSO*. 


REACTIONS  OF  THE  ACIDS. 


(§281 


Hydriodic  acid  and  soluble  iodides  give  with  silver  nitrate  a 
greenish  yellow  precipitate  of  silver  iodide;  insoluble  in 
ammonia  and  in  dilute  acids;  soluble  in  sodium  thiosulphate 
solution.  This  precipitate  does  not  readily  darken  on  expos- 
ure to  the  light. 

277*  Hydriodic  acid  or  a  soluble  iodide,  when  treated 
with  chlorine-water  or  bromine-water,  turns  brown  from  the 
separation  of  free  iodine. 

HI  +  Cl  =  HC1  +  I  -  '         v;, 

HI  +  Br  =  HBr  +  I 

The  iodine  set  free  in  this  reaction  may  be  identified  either 
by  the  addition  of  a  few  drops  of  dilute  starch  paste,  with 
which  it  gives  a  blue  coloration,  or  by  shaking  with  chloro- 
form in  which  it  dissolves  with  a  violet  color. 

An  excess  of  the  chlorine  or  bromine  alters  the  reaction, 
iodine  bromide  or  chloride  being  formed,  instead  of  free 
iodine.     (Compare  equation  §254.) 

HI  +  2CI  =  HCl  +  ICl 

278.  A  soluble  iodide,  when  treated  with  a  ferric  salt, 
liberates  iodine,  which  may  be  recognized  as  above. 

Fe2(S04)3  +  2KI  =  K2SO4  +  2FeS04  +  I3 
By  boiling  the  mixture,  the  whole  of  the  iodine  may  be 
expelled  with  the  steam.  -  -    ;' 

279.  Any  oxidizing  agent,  when  added  to  an  acidified 
solution  of  an  iodide,  sets  the  iodine  free.  Among  the  many 
oxidizing  agents  suitable  for  this  purpose  may  be  mentioned 
KjCrjOT,  KMn04,  MnOj,  NaNO^ 

280.  A  solution  of  an  iodide  is  oxidized  by  warming  with 
concentrated  sulphuric  acid,  the  iodine  being  set  free. 

2KI  +  2H2SO4  =  K2SO4  +  HjSOa  +  I2  = 
K2SO4  +  I2  4-  H2O  +  SO2 
or  6KI  -f-  4H2SO4  =  3K2SO4  -f  3I2  +  S  -f  4H2O 

Concentrated  nitric  acid  also  liberates  iodine  from  iodides. 

281.  A  somewhat  concentrated  solution  of  a  soluble 
iodide  gives  with  lead  nitrate  a  characteristic,  beautiful  yellow, 
crystaP'ne  precipitate  of  lead  iodide,  Pblj.  This  reaction  is 
characteristic,  but  not  very  delicate.  Sulphates  interfere 
with  it. 


',.„iu«S,  ,:..,i». 


■1^ 


1  with  silver  nitrate  a 

iodide;    insoluble   in 

sodium  thiosulphate 

ly  darken  on  expos- 

iodide,  when  treated 
rns  brown  from  the 


I 


y  be  identified  either 

te  starch  paste,  with 

shaking  with  chloro- 

olor. 

e  alters  the  reaction, 

Tied,  instead  of  free 

ICl  ''  '^''"'' 

ed  with  a  ferric  salt, 
;d  as  above. 
2FeS04  +  la 
jf  the  iodine  may  be 

added  to  an  acidified 
e.  Among  the  many 
ose  may  be  mentioned 

lized  by  warming  with 
aeing  set  free. 

SO2 
3I2  +  S  +  4H2O 
J  iodine  from  iodides, 
solution   of    a   soluble 
jristic,  beautiful  yellow, 
Pbla-    This  reaction  is 
Sulphates    interfere 


I 


§387]  ACIDS  OF  THE  FOURTH  GROUP.  6I 

■     "  Hydrocyanic  Acid  and  Cyanides,  RCN. 

282.  Free  hydrocyanic  acid,  HCN,  is  a  feebly  acid  and 
very  volatile  liquid,  the  solutions  of  which  readily  undergo  iicN. 
decomposition.    The  free  acid  and  simple  cyanides  are  deadly 
poisons  and  must  be  handled  with  care.     A  soluble  simple 
cyanide,  if  treated  with  a  ferrous  salt,  then  rendered  alkaline 

and  boiled,  forms  a  ferrocyanide.  The  latter,  on  acidification 
with  hydrochloric  acid  and  treatment  with  a  ferric  salt,  gives 
Prussian  blue  (z'.  §238).  '    '  *' 

6KGN  +  FeS04  =  K2SO4  +  K4Fe(CN)e 

283.  The  simple  cyanides  give  upon  tiic  addition  of 
silver  nitrate  in  nitric  acid  solution  a  curdy,  white  precipitate  silver 
of  silver  cyanide,  Ag2(CN)j.  This  precipitate  does  not  turn  cyanide, 
dark  on  exposure  to  the  light  (in  contra-distinction  to  silver 
chloride).  It  is  soluble  in  ammonia  and  in  an  excess  of 
potassium  cyanide.  It  may  be  dissolved  and  decomposed  by 
prolonged  boiling  with  concentrated  nitric  acid. 

284.  A  simple  cyanide  is  converted  into  a  sulphocyanate 
by  fusion  with  sulphur,  or  if  its  solution  is  boiled  with  yellow 
ammonium  sulphide.  If  after  this  treatment  it  is  ^acidified 
with  hydrochloric  acid,  then  boiied  and  treated  with  ferric 
chloride,  a  blood-red  color  is  produced. 

'  GROUP  IV.  - 

TARTARIC   ACID    AND    TARTRATES. 

285.  Tartaric  acid  is  a  crystalline  solid,  very  soluble  in 
water.  It  fuses  at  135°  and  when  heated  to  a  higher  tem- 
perature decomposes,  giving  off  the  odor  of  burnt  sugar. 
Tartrates  when  heated  give  a  similar  odor. 

a86.  Tartaric  acid  prevents  the  precipitation  of  copper 
and  ferric  salts  by  potassium  hydrate.   When  a  copper  solution  \    ■ 

is  mixed  with  tartaric  acid  and  an  excess  of  potassium  hydrate, 
a  deep  blue  solution  is  formed  but  no  precipitate. 

287,     If  a  solution  of  a  tartrate  is  mixed  with  potassium  „cream 
acetate  and  then  acidified  with  acetic  acid,  a  crystalline  pre-  of  tartar." 
cipitate  of   acid  potassium    tartrate,  KHC4H4O6,  is  thrown 
down  {v.  §34)' 


■■% 


f 


'     t 


"tut 


63 


REACTIONS  OF  THE  ACIDS. 


[8294 


'«';■ 


11^^^ 


288.  Neutral  solutions  of  tartrates  are  precipitated  by 
calcium  chloride  as  calcium  tartrate,  CaCiHiOa  4-  4K8O,  or 
by  barium  chloride  as  BaC4H408  +  HjO. 

The  calcium  salt  is  much  more  insoluble  than  the  barium 
salt.  It  dissolves  in  sodium  or  potassium  hydrate  and  is 
somewhat  soluble  'n  the  presence  of  ammonium  salts. 

GROUP  V. 

289.  Acids  which  give  no  precipitate  with  the  group- 
reagents,  barium  chloride,  silver  nitrate,  or  potassium  acetate. 

Acetates,  Nitrates,  Chlorates. 

290.  The  addition  of  sulphuric  acid  to  an  acetate  sets  free 
Acetates,  acetic  acid,  recognizable  by  its  refreshing,  sour  odor.     If  con- 
centrated sulphuric  acid  be  added  to  three  times  its  volume  of 
alcohol,  and  the  mixture  gently  warmed  with  an  acetate,  a 
peculiar  fruity  odor  of  ethyl  acetate  may  be  observed. 

291.  Acetates  give,  in  concentrated  solutions  only,  when 
treated  with  silver  nitrate,  a  precipitate  of  silver  £  cerate. 

Nitric  acid.  292.  Free  nitric  acid  is  a  most  powerful  acd,  which 
gradually  turns  yellow  when  exposed  to  the  light. 
2HNO8  =  H2O  +  N2O4  +  O 
It  has  the  property  of  turning  many  kinds  of  animal  matter 
yellow,  such  as  skin,  finger  nails,  goose-quill,  cooked  albumen ; 
a  color  which  is  deepened  by  the  subsequent  application  of 
ammonia. 

293.  Nitric  acid  maj'  be  set  free  from  a  nitrate  by  the 
addition  of  concentrated  sulphuric  acid.  If  a  nitrate  be  mixed 
with  equal  volumes  of  concentrated  sulphuric  acid  and  of 
water  and  then  boiled  with  a  quill  tooth-pick,  the  latter  will 
turn  yellow.  As  a  confirmatory  test,  it  may  be  removed  from 
the  solution,  washed  and  dipped  in  ammonia,  when  the  color 
will  change  to  an  orange. 

294.  If  a  nitrate  be  mixed  with  a  solution  of  ferroup 
sulphate  and  the  mixture  be  poured  carefully  upon  concen- 
trated sulphuric  acid  in  a  test-tube,  so  as  to  form  two  layers,  a 
violet-brown  ring  will  appear  at  the  juncture  of  the  two 
liquids.     This  reaction  is  very  delicate.     (Compare  §315-) 


"Xantho 

proteic" 

reaction. 


>jsSi!^^feiajsii,, 


M,  ','5^ , 


*,» 


5.  f§294 

are  precipitated  by 
C4H4O8  4  4KaO,  or 

ible  than  the  barium 
um  hydrate  and  is 
imonium  salts. 


ate  with  the  group- 
er potassium  acetate. 

lATES.  V-'-'-'Si  Ji 

0  an  acetate  sets  free 
r,  sour  odor.  If  con- 
:e  times  its  volume  of 
:d  with  an  acetate,  a 

be  observed. 
.  solutions  only,  when 
)f  silver  acetate, 
powerful  acd,  which 
the  light. 

u  +  0       '---■''■■^' 

Linds  of  animal  matter 
quill,  cooked  albumen; 
(sequent  application  of 

from  a  nitrate  by  the 

If  a  nitrate  be  mixed 

sulphuric  acid   and  of 

th-pick,  the  latter  will 

may  be  removed  from 
iTionia,  when  the  color 

a  solution  of  ferrou? 
carefully  upon  concen- 
is  to  form  two  layers,  a 

1  juncture  of   the   two 
,     (Compare  §315-) 


§300] 


ACIDS   OF  THE  FIFTH  GROUP. 


63 


Iodides  interfere  with  the  reaction.  Should  an  iodide  be 
originally  present,  it  must  first  be  removed  by  boiling  the 
solution  with  ferric  sulphate  (§278). 

295.  If  a  solution  of  a  nitrate  be  mixed  with  its  own  ^^.j^^^jj^ 
volume  of  concentrated  sulphuric  acid  and  if,  to  the  still  hot  j^jion  ^i 
mixture,  a  few  drops  of  indigo  solution  be  added,  the  blue  nitric  acid, 
color  of  the  latter  will  rapidly  change  to  yellow.     Acids  of 
Division  II,  Group  III,  interfere  with  this  reaction. 

296.  If  a  dry  nitrate  be  fused  on  charcoal,  deflagration 
will  ensue. 

297.  Free  chloric  acid  is  a  powerful  acid,  stable  in  dilute 
solutions,  unstable  in  concentrated.  When  treated  with  con- 
centrated sulphuric  acid  a  chlorate  turns  yellow,  from  the 
separation  of  chlorine  tetraoxide,  CljO^,  etc. 

2KCIO8  +  H2SO4  =  K2SO4  -h  HaO  +  Clj04  +  O  Chlorate. 

The  Clj04  is  evolved  as  a  yellow  gas,  of  penetrating  odor, 
which  explodes  when  touched  with  a  hot  wire  and  which 
rapidly  bleaches  a  drop  of  indigo  solution  suspended  in  it  on  a 
glass  rod.  It  is  dangerous  to  pour  sulphuric  acid  upon  potas- 
sium chlorate  in  any  vessel  larger  than  a  test-tube.^ 

298.  If  a  chlorate  be  treated  with  indigo  and  dilute 
sulphuric  acid,  the  indigo  will  not  be  bleached,  but  if  much 
concentrated  acid  be  added,  bleaching  will  occur.  This 
behaviour  distinguishes  the  chlorates  from  the  chlorites  and 
hypochlorites  (§§247-249), 

If  to  the  slightly  acidified  solution  containing  indigo  and  a  Bleaching 
chlorate,  a  small  quantity  of  sodium  sulphite -be  added,  bleach-  ^^ f^  °" 

.    .  .  1  ,  J         rates. 

ing  ensues;  a  characteristic  reaction,  dependent  upon  a  reduc- 
tion of  the  chlorate  to  a  chlorite. 

299.  A  chlorate  gives  no  precipitate  with  silver  nitrate, 

but,  if  it  is  first  fused  on  platinum  foil,  it  will  be  converted  into  0°"^,"^^°^" 
a  chloride  and  the  product  when  dissolved  and  treated  with  into  chio- 
silver  nitrate  will  give  a  precipitate  of  silver  chloride.  fides. 

300.  If  a  dry  chlorate  be  fused  on  charcoal,  deflagration 
will  ensue.  If  a  dry  chlorate  be  heated  in  a  tube  closed  at 
one  end,  oxygen  will  be  evolved,  which  may  be  detected  by 
the  aid  of  a  glowing  splinter. 


-2 


'■J 


4 


iWSt 


"T' 


'•^''•aimmmmmmmmtimammsmk 


^  w-'lP^if's^i;^  "-■%-*!■!»   "»at  ' 


iM' 


CHAPTER   IV. 


SYSTEMA   1^  COURSE  OF  ANALYSIS  FOR  THE 
DETECTION  OF  ACIDS  AND  BASES. 


Three 


analysib. 


PRELIMINARY  EXAMINATION. 
on  I      The  analysis  of  a  solution,  concerning  the  nature  of 
which  we  have  no  clue,  is  naturally  divided  into  three  divi- 
sions-  ist,the  prelim'nary  examination;    2d,  the  detection  of 
Te  adds;'  3^  tL  detectio'n  of  the  bases.     The  object  oth^ 
preliminary  examination  is  to  obtam,  by  means  of  a  few  tests, 
•^ll:;;^  readily  applied,  some  insight  into  the  nature  of  the  substance. 
The  knowledge  gained  in  this  way  often  modihes  and  simpli- 
fies the  analysis.     So,  for  example,  if  we  find  in  the  prehmmary 
examination  that  a  solvation  contains  sodium  carbonate    we 
know  at  once  that  all  those  bases  which  are  precipitated  b> 
alkaline  carbonates  must   be  absent,  and  that  therefore    the 
labor  of  looking  for  them  may  be  spared.     To  get  the  tuU 
benefit,  which  the  preU.ninary  examination  may  afford,  requires 
the  most  thoughtful  attention,^  but  it  should  oji  no  account  be 
be  omitted  or  slighted.     On  tiie  other  hand,  it  should  not  be 
forgotten  that  only  indicaHons  can  be  given,  as  a  rule,  b^^  the 
preliminary  examination  and  that  often  the  reactions  of  differ- 
ent substances  present  will,  more  or  less  completely,  alter  or 

conceal  one  another.  .      .,     •  j- 

In  general,  it  is  necessary  to  receive  with  caution  t^^mdica- 

iTable  III  shows  which  bases  fcrm  soluble,  and  which  insoluble,  sn't.,  with 
each  acid,  and  it  will  be  found  a  useful  guide  to  the  student  in  f,us  cpnnect.on. 


T^. 


IV. 

LYSIS  FOR  THE 
ND  BASES.         '  . 


ATION. 

ncerning  the  nature  of 
vided  into  three  divi- 
;  2d,  the  detection  of 
3.     The  object  of  the 

means  of  a  few  tests, 
iture  of  the  substance. 
;n  modifies  and  simpli- 
;  find  in  the  preliminary 
sodium  carbonate,   we 
ich  are  precipitated  by 
ind  that  therefore,  the 
ared.     To  get  the  full 
ion  may  afford,  requires 
lould  qn  no  account  be 
hand,  it  should  not  be 
given,  as  a  rule,  by  the 

the  reactions  of  differ- 
less  completely,  alter  or 

with  caution  the  indica- 


r>d  which  insoluble,  sn't*,  with 
the  student  in  t'.iis  connection. 


PRRUMINARY  BXAMtff ATION. 


6r, 


"ons  of  the  preliminiry  "xam'iiation  is  to  the  presence  or 
.iiflence  of  ceitain  basei..  or  acids  and  to  confirm  the  results  by 
iipplyikig  further  teits. 

Should  tht  substance  to  be  an  ah  ted  not  be  already  di.s-  Analysis 
lived,  lirections  for  bringing  it  'nto  solution  will  be  found  in  of  solids. 

§348  and  §379- ■  .^    , 

A  p' i-tiop  o.  the  material  on  hand  for  analysis  should  always 

be  set  aside  and  reserved  to  guard  against  unforeseen  accidents 
and  to  use  for  special  or  confirmatory  tests  after  the  whole  of 
the  regu  .ir  course  of  analysis  is  gone  over. 

FLAME  TEST. 

302.  Dip  a  fine  platinum  wire»  into  the  substance  and 
hold  it  in  the  hottest  part  of  the  flame  of  a  Bunsen  burner 
(Fig.  I,  d;  p.  7),  and  observe  the  color  of  the  flame.  If  the 
substance  is  a  solid,  it  may  be  advantageous  to  moisten  it  with 
hydrochloric  acid  previous  to  bringii.  j'  it  into  the  flame,  fc. 
the  reason  that  the  chlorides  of  some  bases  are  more  volati)- 
and  impart  a  more  pronounced  color  to  the  flame  than  the  free 
bases  or  their  oxy-salts. 

The  following  elements  and  their  compounds  afford,  under 
the  given  co.iditions,  more  or  less  characteristic  indications. 


Potassium 
Barium: 
Boric  Acid: 
Coi'pkr: 
Phosphorus  or 
Phosphites  : 
Sodium  : 

Calcium:  .   " 

Strontium  : 
Lithium: 

Arsenic  (or  Zinc)  : 
Copper  Chloride: 
Antimony  : 


The  flame  is  violet, 
green, 


■#■ 


(( 


(( 


I* 

'Tti 


green,        .     . 
green,        .     . 

pale  green, 
bright  yellow . 
orange,      .     . 
crimson,     .     . 
crimson, 
pale  blue, 
bright  blue,     . 
greenish  blue. 


§35 
§51 
§225 
§145 


§28 
§43 
§47 


§H5 
§174 


iThe  platinum  wire  must  first  be  so  thoroughly  cleaned  that  it  will  not  color 
the  flame  when  held  in  it  {v.  §7,  p.  7). 


'(^■:<.^:^.):^ 


m. 


VW 


Fusion  on 
charcoal. 


66  SrSTEAfAT/C  A.VALrSrS.  [8304 

EXAMINATION  IN  MATRASS  AND  OPEN  TUBE. 

303*  This  part  of  the  preliminary  examination  ii,  of 
course,  directly  applicable  only  to  solids.  It  is  not  usually 
worth  while  to  evaporate  a  solution  to  dryness  in  order  to  test 
the  b.jhaviour  of  the  residue  in  the  matrass  or  in  the  open  tube. 

'..  lie  closed  tube  is  described  in  ^^14,  where  a  list  of  the  most 
characteristic  reactions  which  may  be  observed  by  its  aid  may 
be  found. 

It  should  be  made  of  very  hard,  difficultly  fusible,  thin  glass, 
and  it  may  be  from  three-sixteenths  to  three-tenths  of  an  inch 
in  external  diameter,  three  to  four  inches  being  the  most  suit- 
able length.     For  the  indications  of  the  open  tube  see  §i5- 

REDUCTION  TEST. 

304.  If  the  substance  is  a  solution,  this  part  of  the 
preliminary  examination,  like  the  foregomg,  is  not  directly 
applicable.  If  it  is  solid,  moisten  it  with  a  drop  of  water  and 
rub  it  up  on  a  card  to  a  stiff  paste,  using  a  pen-knife  blade  to 
incorporate  the  ingredients.  Roll  the  mixture  into  the  form 
of  a  pellet;  place  it  in  a  hollow  on  the  charcoal  stick,  and 
fuse  in  the  reducing  flame  for  several  minutes  (§§12,  165). 
Dig  out  the  mass,  place  it  on  a  silver  coin  and  moisten  it. 
The  formation  of  a  black  stain  on  the  silver  indicates  sulphur, 
a  sulphide,  sulphite,  sulphate,  thiosu'phate  or  a  sulphocyanate. 
Carefully  examine  the  fused  mass  for  metallic  globules  or 
particles.  To  this  end,  it  is  sometimes  well  to  rub  it  up  in  a 
mortar  with  a  little  hot  water  and  then  to  allow  a  current  of 
water  from  the  wash-bottle  to  run  through  and  over  the 
residue.  Under  this  treatment  the  powdered  charcoal  can  be 
washed  away,  leaving  the  heavier  metallic  particles,  if  any,  in 
Separiition  ^^^  mortar.     Under  the  pestle,  globules  of  any  malleable  metal 

of  reduced         .,    ,  ,    .  ,..,.,  ,        .  ,  ,  r 

metal.  w)ll  be  pressed  mto  little  disks  or  lumiiice,  whereas  those  01 
brittle  metals,  such  as  bismuth,  will  be  broken  into  crystalline 
fragments.     If  a  metal*  has  been  reduced  it  may  be: 


Detection 
of  Rulptiur. 


> Consult  Chapter  II  for  suitable  confirmatory  tests  for  any  of  the  metals 
enumerated.  The  metallic  particles  obtained  may  be  examined  by  the  blow- 
pipe .iccording  to  the  scheme  laid  down  in  Table  I. 


|)  OPEV  TUBE. 

examination  is,  of 
IS.  It  is  not  usually 
ryness  in  order  to  test 
|s8  or  in  the  open  tube, 
/here  a  list  of  the  most 
bserved  by  its  aid  may 

Itly  fusible,  thin  jjlass, 
hree-tenths  of  an  inch 
3  being  the  most  suit- 
open  tube  see  §15. 


ion,  this  part  of  the 
gomjf,  is  not  directly 
;h  a  drop  of  water  and 
ig  a  pen-knife  blade  to 
mixture  into  the  form 
he  charcoal  stick,  and 
1  minutes  (^12,  165). 
T  coin  and  moisten  it. 
silver  indicates  sulphur, 
ate  or  a  sulphocyanate. 
r  metallic  globules  or 
J  well  to  rub  it  up  in  a 
1  to  allow  a  current  of 
through  and  over  the 
.'dered  charcoal  can  be 
dlic  particles,  if  any,  in 
1  of  any  malleable  metal 
ii)i(F^  whereas  those  of 
broken  into  crystalline 
;ed  it  may  be: 


tests  for  any  of  the  metals 
y  be  examined  by  the  hlow- 
I. 


PRBUMINARY  EXAMINATION. 

Lkau:  The  globule  is  very  soft. 

Antimony:  «'         «•           brittle,  crystalline,  while. 

SiLVKit:  «»        "           white,  malleable. 

Bismuth:  "         ««           gray,  brittle. 

Coim'Kr:  "         »«           red,  malleable. 

Tin:  «♦         ♦«           white,  malleable. 

Ikon:  The  particles  are  gray,  magnetic. 

Nickkl:  The  spangles  are  gray,  magnetic,  infu.sible. 

Cobalt:  "        •«         "         "     magnetic,  infusible. 

SULPHURIC  ACID    TEST. 

305.      Acidify  the  substance,  which  may  be  either  a  solu- 
tion or  a  solid,  with  dilute  sulphuric  acid.     If  a  gas  is  evolved  Reactions 
it  may  indicate: — 

Carbonates:       The  gas  is  COj 


Sulphites: 


SO, 


Thiosulphates:       "       "      SO, 


Sulphides: 

Nitrites: 

Hypochlorites 
and  chlorites 

Simple  cyanides:  " 


-  s 


HaS 

NjOa 

CI2 
HCN 


It  is  odorless  and  renders 
lime-water  milky. 

It  smells  of  burnt  sulphur 
and  turns  a  solution  of 
BaCl2  and  Br  water  tur- 
bid. 

As  with  sulphites,  but  sul- 
phur is  set  free. 

It  has  a  characteristic  odor 
and  blackens  lead  paper. 

Brown  fumes. 

Yellow  gas,  characteristic 
odor. 


with  dilute 
H,SO«. 


Colorless  vapour  of  char- 
acteristic odor,  precipi- 
tates solution  of  AgNOg. 

Silicates  :  No  gas  liberated,  but  in  some  cases  the  solution 
gelatinizes. 

Reactions 

Then  boil  the  mixture,  if  necessary,  until  odorless  and,  when  witii  con- 
cold,  add  twice  its  volume  of  concentrated  sulphuric  acid,  centrated 
Observe  any  reaction  that  occurs  either  at  once  or  on  heating  "»^^*- 


i 


*.% 


58  SrSTEMATiC  ANALrS/S.  |§3o«'' 

to  the  boiling  point.     The  following  bodies  exhibit  charac- 
teristic phenomena. 

ReactionN 

with  con-  Oxalates:     .     .    .     Give  CO,  and  CO,  turns  lime-water 

ccntrated  milky. 

H1SO4.      Chlorides:      ...        ♦♦    HCl,  turns  silver  nitrate  milky. 

Bromiuks:     ....      «•    HBr,  and    Br,  gas  is   brownish, 

bleaches  indigo  and  precipitates 
silver  nitrate. 

Iodides: "    iodine,  violet  vapours. 

Nitrates:  ....        ••    occasionally  light  brown  vapours, 

strongly  acid. 

Chlorates:     ...        ««    Cl,|04,  bright  yellow,   explosive 

gas. 
Acetates:     ...  "    odor  of  acetic  acid. 

Compound  cyanides:       "    CO,  burns  with  pale  blue  flame. 
SuLPHOCYANATEs:      .       "    COS,  peculiar  odor.    Bums  with 

blue  flame  giving  odor  of  SO3. 

Fluorides:     ...         "    HF,  a  colorless,  suffocating  gas 

which  etches  the  tube.* 

Organic  matter:     .    Substance  turns  black  or  brown. 

Silicates:     .     .     .     •   The  substance  gelatinizes  (but  not  in 

all  cases). 

EXAMINATION  FOR  THE  ACIDS. 
GENERAL  REMARKS. 

306.  It  is  impracticabiL:  u\  reduce  the  examination  for  the 
acids  to  so  complete  a  system  as  that  which  is  followed  in 
detecting  the  bases,  or  to  arrange  any  course  of  procedure. 
System,  which  would  enable  us  test  for  all  the  acids  consecutively  in 
one  portion  of  the  solution.  Instead  of  this,  it  is  in  general 
necessary  to  test  different  portions  of  the  material  for  the 
various  acids.     Nevertheless,  by  following  a  systematic  and 

*The  etching  can  often  be  seen  only  after  the  tube  is  washed  and  dried. 


»» 


llics  exhibit  charac- 

),  turns  lime-water 

plver  nitrate  milky. 

ir,  gas  is  brownish, 
Idigo  and  precipitates 
Ite. 

vapours. 

light  brown  vapours, 
dd. 

It   yellow,   explosive 

ic  acid. 

with  pale  blue  flame, 
iar  odor.  Bums  with 
e  giving  odor  of  SOj. 

»rless,  suffocating  gas 
;hes  the  tube.* 

black,  or  brown. 

gelatinizes  (but  not  in 

ACIDS. 

:s. 

le  e.xamination  for  the 

which  is  followed  in 

course  of  procedure, 

acids  consecutively  in 

jf  this,  it  is  in  general 

the  material  for  the 

ring  a  systematic  and 

)e  is  washed  and  dried. 


»307] 


DRTBCT/OX  OF  TUB  ACIDS, 


69 


orderly  mode  of  procedure,  the  results  are  both  more  certain 
and  more  quickly  reached. 

Two  different  schemes  are  lO  be  followed,  according  to 
whether  a  precipitate  forms  in  the  solution,  when  it  is  care- 
fully neutralized  with  ammonia,  or  not.  If  no  precipitate  is 
produced  upon  neutralization,  we  are  thereby  assured  of  the 
absence  from  the  solution  of  any  salt  insoluble  in  neutral  solu- 
lutions  [v.  Table  III).  If,  on  the  other  hand,  a  precipitate 
forms  when  the  solution  is  made  neutral,*  the  simplest  plan  is 
to  first  remove  all  those  bases  which  could  form  precipitates 
with  any  of  the  acids  present.  We  accordingly  proceed  as 
follows. 

Add  enough  ammonia  to  a  portion  of  the  solution  to  render 
it  just  neutral.     If  no  precipitate  forms,  pass  to  §307. 

If  a  precipitate  is  formed,  add  to  the  main  part  of  the  solu- 
tion a  considerable  excess  of  sodium  carbonate  and  boil  in  a  Reinov.il 
porcelain  dish.     The  precipitate  will  contain  all  the  bases  of  ofi)inie»o< 


the  second,  third,  fourth  and  fifth  groups,  and  possibly,  phos- 
phoric acid.  Filter  the  solution  and  test  the  filtrate  f  the 
acids  according  to  the  following  sections,  beginning  at  §307. 

Wash  the  precipitate  until  the  washings  no  longer  exhibit 
an  alkaline  reaction  and  examine  it  for  phosphoric  acid,  as 
follows.  Transfer  it  while  yet  moist  to  a  test-tube  and  shake 
with  ammonium  sulphide.  Allow  it  to  stand  for  some  time  in 
a  warm  place,  filter,  boil  the  filtrate,  filter  from  separated  sul- 
phur and  then  add  ammonia,  ammonium  chloride  and  magne- 
sium chloride  [v.  §211).  The  appearance  of  a  colorless 
crystalline  precipitate  indicates  phosphoric  acid.  The  confir- 
matory test  with  AgNOa  should  be  applied. 

In  testing  for  the  acids  of  Groups  I,  III  and  V,the  treatment 
with  sodium  carbonate,  described  above,  is  not  necessary  and 
in  the  case  of  Group  V  it  is  better  to  omit  it. 

GROUP  I. 

307.  Acid'- V  a  part  of  the  solution  slightly  (§192)  with 
hydrochloric  ac  d  and  add  a  drop  of  barium  chloride.     If  a 


l)igiiei' 
groups. 


*The  best  means  o£     ^certaining  the  point  of  neutralization  is  by  the  use  of 
lacmoid  paper  (§24). 


i\ 


,->aSl»>?;;^  .     'MW:^. 


—<:r..s3Xt'i^:iC^ 


VI. 


70 

Sulphuric 
acid;  its 
detection 
and  re- 
moval. 


SrSTEMATIC  ANAL r SIS. 


i§3o8 


white,  finely  divided  precipitate  forms,  sulphuric  acid  is 
present.  Should  a  precipitate  be  produced  by  hydrochloric 
acid,  the  solution  must  be  filtered  before  adding  the  barium 
chloride. 

If  sulphuric  acid  is  found,  add  barium  chloride  gradually 
until  it  produces  no  further  precipitate.  Filter,  and  test  thj 
filtrate  by  the  addition  of  one  more  drop  of  barium  chorije,  to 
make  dure  that  all  the  sulphuric  acid  is  removiid.  Examine 
the  clear  filtrate  for  the  acids  of  the  second  group  according  to 
the  following  paragraph. 

GROUP  II. 

308.  Neutralize  carefully  with  ammonia  the  solution  from 
which  sulphuric  acid  has  been  removed  (or  a  part  of  the  orig- 
inal solution  (§306)  in  case  it  contained  no  sulphates)  and  add 
barium  chloride,  if  it  has  not  already  been  added  in  the  opera- 
tions of  the  foregoing  section. 

If  no  precipitate  forms,  all  acids  of  the  second  group  are 
absent.^     Pass  to  §312. 

If  a  precipitate  appears,  some  acid  of  the  second  group  is 
present.  If  the  precipitate  is  yellow,  a  chromate  is  probably 
present,  if  colorless,  absent. 

The  preliminary  sulphuric  acid  test  (§305)  will  have  shown 
whether  any  acids  of  the  first  division  of  this  group  are  present 
and,  if  so,  which  of  them ;  except  in  complex  mixtures,  when 
all  must  be  sought  for. 

If  the  substance  evolved  a  gas,  when  treated  with  dilute  or 

concentrated  sulphuric  acid,  it  must  be  examined  for  all  acids 

of  Division  I,  according  to  §§194  to  209,  unless  the  preliminary 

examination  gave  unmistakable  indications  as  to  which  are 

present  and  which  absent. 

Acids  of        In  either  case,  examine  a  portion  of  the  original  solution  (or 

the  fecond  that  treated  with  sodium  carbonate,  §306)  as  follows,  for  acids 

division.    ^£  Division  II,  bearing  in  mind  that  a  chromate  would  have 


Acids  of 
the  first 
division. 


> Carbonic  acid  may  have  been  expelled  and  lost  during  the  operation  of  sep- 
arating the  sulphuric  acid.  This  is  of  no  practical  importance,  since,  if  present, 
it  would  have  been  detected  hy  the  '•  Sulphuric  Acid  Test"  during  the  prelimi 
nary  examination. 


We: 


L. 


snlfhuiic   acid    is 
|ced  by  hydrochloric 
adding  the  barium 

chloride  gradually 

Filter,  and  test  thj 

|of  barium  choride,  to 

removed.     Examine 

id  group  according  to 


jonia  the  solution  from 

(or  a  part  of  the  orig- 

no  sulphates)  and  add 

en  added  in  the  opera- 

the  second  group  are 

of  the  second  group  is 
chromate  is  probably 

^§305)  will  have  shown 
if  this  group  are  present 
omplex  mixtures,  when 

;n  treated  with  dilute  or 
I  examined  for  all  acids 
•fi  unless  the  preliminary 
ations  as  to  which  are 

the  original  solution  (or 
06)  as  follows,  for  acids 
I  chromate  would  have 


8t  during  the  operation  of  sep- 
il  importance,  since,  if  present, 
V.cid  Test"  during  the  prelimi 


Silicates. 


Pliosphateg. 


DETECTION  OF  THE  ACIDS. 

been  indicated  by  the  color  of  the  precipitate,  and  the  pre- 
liminary examination  would  have  revealed  the  presence  of 
silicates,  unless  present  only  in  minute  quantity. 

309.  If  the  preliminary  examination  (§305)  showed  the 
presence  of  a  silicate,  the  silicic  acid  must  be  removed  by  the 
method  given  in  §230.  Since  small  amounts  of  SiOj  may  be 
overlooked  by  the  method  of  §305,  it  is  desirable,  in  exact 
analyses  to  carry  out  the  process  of  §230  in  ali  cases. 

The  solution  filttred  from  the  insoluble  silica  is  to  be  used 
for  the  following  reactions. 

310.  Neutralize  the  solntJon,  free  from  silicic  acid,  with 
'Ummonia,^  add  magnesium  chloride  and  then  an  excess  of 
ammonia.  Allow  it  to  stand  for  several  hours.  A  colorless, 
crystalline  precipitate  indicates  a  phosphate  or  an  arsenate 
(§§212-216).  To  distinguish  between  them,  filter,  wash  the 
precipitate  thoroughly  and  moisten  it  with  silver  nitrate  solu-  Arsenates. 
tion.  If  it  turns  yelloiv  a  phosphate  is  present,  if  brick-red^  an 
arsenate. 

311.  Test  a  portion  of  the  original  solution  for  boric  acid 
by  §225  or  §226. 

GROUP  III. 

312.  Acidify  a  portion  of  the  original  solution,  or  that 
which  was  treated  with  sodium  carbonate  by  §306,  with  dilute 
nitric  acid  and  add  a  drop  of  silver  nitrate. 

If  no  precipitate  forms,  all  acids  of  the  third  group  are 
absent.     Pacs  to  §3?i.  '  ■  • 

If  a  pi  ricipitate  is  produced,  test  for  the  acids  of  Divisions 
I,  II,  III  and  IV  of  this  group,  as  follows.  , 

Division  I. 

313.  Acidify  a  portion  of  the  solution  with  hydrochloric 
acid  and  add  ferric  sulphate  (§235). 

If  the  solution  does  not  change  color,  no  acid  of  this  division 
is  present.     Pass  to  §314. 

'Ammonium  ciiloride  must  be  added  if  it  is  not  already  present;  but  if  a 
liydrochloric  acid  solution  has  been  neutralized  with  ammonia,  further  addition 
of  an  ammonium  salt  is  usually  superfluous. 


Borates. 


m 


t 


^m^m 


III 


Vik. 


72 


SYSTEMATIC  ANALYSIS. 


[83'6 


cyanides. 


Hypo- 
chlorites 


Nitrites. 


If  it  becomes  red  a  sulphocyanate  is  present;  if  deej>  blue,  a 
CompoMnA  j-grrocyanidc.     If  it  turns  reddish  brown,  add  ferrous  sulphate 
which  will  produce  a  deep  blue  in  the  presence  of  ^  ferri- 
cyanide. 

Division  II. 

314.  Mix  a  portion  of  the  solution  with  a  few  drops  of 
dilute  indigo  solution,  then  add  a  considerable  excess  of  dilute 
sulphuric  acid  and  boil  (§246).  If  the  indigo  does  not  lose 
its  color,  acids  of  this  division  arc  absent.     Pass  to  §316. 

If  the  indigo  is  bleached,  proceed  as  follows. 

Render  a  portion  of  the  original  solution  slightly  alkaline 
with  sodium  carbonate  and  add  dilute  indigo  solution.  If  it 
is  bleached,  a  hypochlorite  is  indicated.  Confirm  by  one  or 
more  of  the  tests  given  in  §§247-249. 

Regard  must  be  had  to  the  possible  presence  of  a  free 
haloid  (§§251-258). 

315.  Add  a  few  drops  of  dilute  sulphuric  acid  to  a  solu- 
tion of  ferrous  sulphate,  then  add  cautiously  a  portion  of  the 
original  solution,  so  as  to  form  a  separate  layer.  A  brown 
ring  will  be  visible  at  the  juncture  of  the  two  layers,  if  a 
nitrite  is  present.     (Compare  §294). 

Ferrocyanides  an:l  ferricyanides  interfere  with  this  reaction. 
If  the  test  of  §314  gave  a  positive  result  (/.  e.  if  indigo  solu- 
tion was  bleached)   and  if  the   tests  for   hypochlorites   and 
Chiorites.  nitrites  gave  negative  results,  a  chlorite  may  be  assumed  to  be 
present.     Confirm  this  conclusion  by  the  reactions  of  §249. 

Division   III. 

316.  If  any  acids  of  this  division  are  present,  the  precipi- 
tate produced  by  silver  nitrate  (§312)  will  be  black  or,  in  the 
case  of  thiosulphates,  will  graduUy  become  black  on  standing 

Sulpliides.  or,  more  quickly,  on  boiling.  The  individual  salts  of  the  acids 
of  this  division,  if  present,  may  be  detected  by  the  reactions 
described  in  §§260  to  268,  but  a  normal  sulphide  can  not  be 
detected  in  the  presence  of  a  polysulphide. 

When  thiosulphates  and  sulphides  are  present  together,  the 

pha°Ll"  *  latter  must  be  removed  before  the  former  can  be  detected 
with  certainty.     To  do  this,  add  ammonia  to  a  solution  of  zinc 


HT' 


[83'6 

sent;  if  deef  blue,  a 
Idd  ferrous  sulphate 
Iresence  of  a  ferri- 


irith  a  few  drops  of 
}able  excess  of  dilute 
Indigc  does  not  lose 

Pass  to  §316. 
llows. 

Ition  slightly  alkaline 
Indigo  solution.     If  it 

Confirm  by  one  or 

presence  of   a  free 

Iphuric  acid  to  a  solu- 

ously  a  portion  of  the 

rate  layer.     A  brown 

If  the  two  layers,  if  a 

fere  with  this  reaction, 
ult  (/.  e.  if  ind'go  solu- 
for  hypochlorites  and 
may  be  assumed  to  be 
e  reactions  of  §249. 

re  present,  the  precipi- 
ivill  be  black  or,  in  the 
)me  black  on  standing 
vidual  salts  of  the  acids 
tected  by  the  reactions 
u  sulphide  can  not  be 
ide. 

e  present  together,  the 
rmer  can  be  detected 
nia  to  a  solution  of  zinc 


§317] 


DETECTION  OF  THE  ACIDS. 


Haloid 
salts. 


chloride  until  the  precipitate  formed  at  first  is  just  redissolved, 
Treat  a  portion  of  the  original  solution  with  an  excess  of  the 
reagent  so  prepared  and  then  filter  from  the  precipitated  zinc 
sulphide.  The  filtrate  will  be  free  from  sulphides,  but  will 
contain  all  the  thiojulphuric  acid  originally  present.  The  latter 
can  be  detected  by  the  reaction  with  hydrochloric  acid  (§266) 
or,  in  the  absence  of  other  reducing  agents,  by  that  with 
iodine  (§268). 

■         .  Division    IV. 

317.  The  detection  of  chlorides,  bromides,  iodides,  and 
cyanides,  when  present  together  in  a  solution,  is  a  difficult 
matter.  When  any  one  of  these  compounds  is  present  it  may 
readily  be  detected  by  the  tests  given  in  §269  et  seq. 

In  case  it  is  desired  to  test  for  all  of  these  compounds,  in 
solutions  containing  two  or  more  of  them,  you  may  proceed  as 
follows:  '- 

Acidify  a  portion  of  the  original  solution  with  acetic  acid  and 
heat  to  boiling.  In  the  escaping  vapoum  hold  a  drop  of  silver  Cyanides, 
nitrate,  suspended  on  a  glass  rod,  jr  pass  the  evolved  gas  into 
a  silver  solution.  If  a  precipitate  of  silver  cyanide  is  formed 
in  the  silver  nitrate  solution,  a  cyanide  is  indicated.  In  this 
case  continue  the  boiling  until  the  hydrocyanic  acid,  HCN,  is 
entirely  expelled.  Then  add  a  small  quantity  of  dilute  sul- 
phuric acid  and  an  excess  of  feiric  sulphate.  If  iodine  is  iodides, 
present,  it  will  be  liberated  and  will  make  itself  apparent  by 
the  color  of  the  evolved  vapour  and  by  its  odor  and,  further, 
by  the  starch  paste  reaction  (§259). 

In  case  iodine  is  found,  boil  the  solution  continuously  until 
it  is  entirely  expelled. 

The  solution  will  now  contain  bromides  and  chlorides  and 
will  be  free  from  cyanides  and  iodides.  If  a  precipitate  is 
formed  during  the  boiling,  filter.  Divide  the  filtrate  into  two 
portions:  test  one  portion  fcr  bromides  by  §274;  to  the  other 
portion  add  silver  nitrate.  If  a  perfectly  white  precipitate 
forms,  which  turns  violet  on  ex^josure  to  the  light  a  chloride  is 
present.  If  bromides  are  present  this  precipitate  will  be 
yellowish.     Usually,  howe^'^er,  silver  chloride  can  be  detected 


11 


14. 

I  i 


Bromides. 


i;  1 . 


■>■:;■' 


*MI» 


74 


SrSTEMATlC  ANALrsrs. 


r§32o 


Chlorides. 


Removal 
of  sul- 
phides. 


Detection 
of  cyan- 
ides. 


in  the  presence  of  a  moderate  amount  of  silver  bromide  by  the 
action  of  light  upon  the  former.  In  cases  of  uncertainty  you 
may  have  to  test  a  portion  of  the  solution  for  chlorides 
accort'ing  to  §272.  It  is  very  difficult  to  detect  a  small  quan- 
tity of  a  chloride  in  the  presence  of  a  large  amount  of  bromides. 
Detection  of  Chlorides  in  Presence  of  Cyanides,  Ferrocyanidks, 

SULPHOCYANATBS   AND   FeRRICYANIDBS. 

318.  The  presence  of  simple  and  compound  cyanides 
prevents  "the  recognition  of  chlorine  by  the  silver  nitrate  test. 
A  chloride  may  however  be  detected,  in  the  presence  of  these 
cyanides,  by  boiling  the  precipitate  produced  by  nitrate  of 
silver  for  some  time  with  concentrated  nitric  acid.  Under 
thifi  treatment  all  the  cyanides  will  finally  be  decomposed  and 
dissolved,  silver  chloride  alone  remaining  undissolved. 

Detection  of  the  Acids  of  Division  IV  in  the  Presence  of 

SULPMIDUS. 

319*  When  a  sulphide  or  a  polysulphide  is  present  in  a 
solution  containing  a  chloride,  bromide  or  iodide,  or  all  of 
these,  it  must  be  got  rid  of  before  the  latter  can  be  detected. 
For  this  purpose,  add  to  the  solution  ferrous  sulphate  in  slight 
excess,  then  ammonia  in  excess,  boil  for  some  time  in  an  open 
dish  and  filter. 

The  filtrate  will  be  free  from  sulphides  and  can  be  directly 
tested  for  chlorides,  bromides  and  iodides  in  the  usual  w?'". 
In  employing  this  process,  it  is  to  be  remembered  that,  if  the 
original  solution  contained  a  simple  cyanide,  this  will  be  con- 
verted into  a  ferrocyanide  by  the  treatment  described.  It  will 
be  detected  on  acidifying  the  filtrate  and  adding  a  little  ferric 
sulphate  (§97)  which  will  produce  a  precipitate  of  Prussian 
blue.     This  is  the  best  way  of  detecting  a'  cyanide  in  such 

mixtures. 

GROUP  IV.  "  ■      ''     '" 

320.  If  tartaric  acid  were  present  in  the  substance  under 
examination,  the  preliminary  test  with  concentrated  sulphuric 
acid  (§305)  would  have  indicated  organic  matter  by  turning 
the  substance  black.  In  this  case  the  special  tests  for  tartrates 
(§4^286-287)  may  be  applied,  otherwise  they  may  safely  be 
oniittcd 


1 


liver  bromide  bv  the 

of  uncertainty  you 

lution   for   chlorides 

letect  a  small  quan- 

miount  of  bromides. 

|nides,  Fkrrocyanides, 

VNIDES. 

compound  cyanides 
|he  silver  nitrate  test, 
the  presence  of  these 
iduced  by  nitrate  of 

nitric  acid.     Under 

be  decomposed  and 

undissolved. 
IN  THE  Presence  of 

phide  is  present  in  a 
or  iodide,  or  all  of 
atler  can  be  detected. 
Irous  sulphate  in  slight 
some  time  in  an  open 

;s  and  can  be  directly 
,es  in  the  usual  w?-'. 
membered  that,  if  the 
inide,  this  will  be  con- 
ent  described.  It  will 
i  adding  a  little  ferric 
)recipitate  of  Prussian 
ing  a'  cyanide  in  such 


in  the  substance  under 
concentrated  sulphuric 
lie  matter  by  turning 
»ecial  tests  for  tartrates 
e  they  may  safely  be 


DETECTION  OF  THE  ACIDS. 


GROUP  V. 


321,  Except  in  some  complex  mixtures,  nitrates,  chlo- 
rates and  acetates  are  usually  detected  in  the  course  of  the 
preliminary  examination.  But  since  the  detection  of  acetates 
(§305)  depends  upon  the  production  of  an  odor,  it  may  easily 
be  understood  that  the  presence  of  nitrites,  nitrates,  chlorates, 
hypochlorites,  sulphides,  sulphites,  thiosulphates,  chlorides, 
bromides,  iodides,  and  other  substances  which  evolve  a  pow- 
erful odcr  under  the  action  of  concentrated  sulphuric  acid, 
interfere  more  or  less  seriously  with  the  acetic  acid  reaction.      ,    _ 

The  acids  of  the  third  group  may  be  removed  by  treating 

.  ,      .,  ,    ,  .  y  e-y       •  -c^  Separation 

the  solution  with  silver  sulphate  m  excess  and  nitenng.    r  rom  ^£  acetates 
the  filtrate  the  acids  of  the  first  and  second  groups  may,  chlorates, 
similarly,   be   removed  by  treatment  with   barium   hydrate  and  nitrates 
and   subsequent   filtration.      This   filtrate    will   probably  be  ^^"™ 
very  dilute.     It  must  be  boiled  down  to  a  small  volume,  and 
can  then  be  tested  for  acetates  (§290)  which  will  be  readily 
detected,  unless  nitrates  or  chlorates  are  also  present.     In  the 
latter  case,  the  formation  of  basic  ferric  acetate  (§99)*  may 
be  used  to  separate  the  acetic  acid   from  the  nitrates  and 
chlorates.     The  basic  acetate  which  will  be  precipitated  on 
boiling  the  neutral  solution  with  ferric  chloride  (containing  no 
free  acid)  can  be  washed  and  used  for  the  test  of  §290. 

In  case  only  one  of  the  acids  of  thi3  group  is  present,  the 
reactions  of  §§290  to  300  will  suffice  for  its  easy  detection  or 
for  confirmation  if  the  preliminary  examination  gave  an  indi- 
cation. 

SYSTEMATIC  COURSE  OF  ANALYSIS  FOR  THL  DETECTION 

OF  THE  BASES. 

GENERAL   REMARKS. 

322.  In  the  systematic  course  of  analysis  for  the  detec- 
tion of  the  bases,  thc'e  are  first  separated,  in  groups  (§25), 
from  one  another,  by  the  aid  of  the  general  group-reagents. 
The  individual  bases  of  each  group  are  then  separated  one 
from  another  by  special  methods,  detailed  in  the  following 
pages. 


?1 

I 

I 


mk 


y^-yjiir .,;  ^  i.'  ^ gnu  n  a  nugajf-ag;? .  ■  ■  - 


76 


ik»' 


SrSTEMATIC  ANALTSIS. 


[»3J4 


323.  In  order  to  make  the  general  principles  of  the  pro- 
cedure clear,  the  following  outline  plan  for  the  separation  of 
the  groups  is  presented. 

/.  Acidify  the  solution  with  hydrochlor'c  acid 
and  add  hydrogen  sulphide  in  excess. 

Groups  V  and  VI  ar?  precipitated  as  sulphides. 

Filter  and  wash.     The  filtrate  contains  Groups  :  ; 

I,  II,  III  and  IV.     Pass  to.'. 

Digest  the  precipitate  with  yellow  ammonium 
sulphide,  filter  and  wash.  The  filtrate  contains 
Group  VI,  the  precipitate  Group  V. 

2.  Add  ammonium  chloride,  then  ammonia 
umtl  alkaline,  th  n  ammonium  sulphide. 

The  precipitate  contains  Group  III  as  hydrates 
and  Group  IV  as  sulphides.  The  filtrate  con- 
tains Groups  I  and  II.     Pass  to  j. 

Treat  the  precipitate  with  dilute  hydrochloric 
acid.  The  residue  contains  I¥i,  Co.  Boil  the 
solution  with  excess  of  potassium  hydrate.  The 
precipitate  contains  Fc,  Ifln,  Cr.  The  filtrate 
contains  Al,  Zn. 

J.  Add  ammonium  carbonate. 

The  precipitate  contains  carbonates  ot  Group  II, 

EXCEPT  MAGNESIUM. 

The  filtrate  contains  magnesium  and  Group  I. 
Add  ammonium  phosphate.  The  precipitate 
contains  lUg;,  the  filtrate,  IVa  and  K. 

SEPARATION  OF  GROUPS   V  AND   VI   FROM   LOWER 

GROUPS. 

324.  Take  a  portion  of  the  solution  which  has  been 
reserved  for  the  detection  of  the  bases  ^  anu  observe  its  odor 


*  Silicic  cr  liydrofluoric  acids,  if  originally  present,  must  be  removed  before 
proceeding  to  the  detection  of  the  bases.  The  methods  of  separation  are  given 
in  §§228,  231.    (Cf.  note  to  §33" ) 


rinciples  of  the  pro- 
lor  the  separation  of 

I  -      ■> 

ic  add 

as  sulphides. 
Itains  Groups 

yellow  ammonium 
The  filtrate  contains 
Group  V. 

imonia 

II  as  hydrates 

,e  filtrate  con- 

r. 

h  dilute  hydrochloric 

ns  I¥i,  Co.    Boil  the 

tassium  hydrate.    The 

In,  Cr.     The  filtrate 


?s  ot  Group  II, 

NEsiuM  and  Group  I. 
ite.      The  precipitate 
I\a  and  K. 

VI   FROM   LOWER 

tion  which   has   been 
anu  observe  its  odor 

it,  must  be  removed  before 
liods  of  separation  are  given 


§3^6] 


DETECTION  OF  THE  BASES. 


77 


and  reaction  with  litmus  or,  better,  with  lacmoid  paper.     If  it 
is  very  strongly  acid,  dilute  it  freely  vith  water,  i     If  neutral,  precipita- 
acidify  slightly   with   hydrochloric   acid.     Then,   no   matter  tion  of  the 
whether  a  precipitate  forms  or  not,  pass  hydrogen  sulphide  '''^''^■>' 
through  the  solution  until  it  smells  strongly  of  the  gas  after 
shaking.     If  no  colored  precipitate  appears,  metals  of    the 
higher  groups  are  absent.     Pass  to  §330.  ' 

If  a  precipitate  forms,  other  than  a  finely  divided,  white  one 
of  sulphur,  it  will  contain  the  metals  of  the  fifth  and  sixth 
groups.  Warm  the  solution  nearly  to  boiling,  filter  and  wash 
as  rapidly  as  possible  v.ith  water  containing  a  little  hydrogen 
sulphide.  The  filtrate  {A)  wiH  contain  any  bases  of  the  first, 
second,  third  and  fourth  groups  which  may  be  present.  Set 
it  aside  for  examination  according  to  §330.  The  treatment  of 
the  precipitate  is  given  in  the  next  paragraph. 

SEPARATION  OF  THE  FIFTH  FROM  THE  SIXTH   GROUP. 

325.  Punch  a  hole  in  the  filter  paper  containing  the  pre-  ^^  the"pr"- 
cipitated  sulphides  and  rinse  the  latter  into  a  test-tube.     Add  c.pitate 
to  it  a  moderate  quantity  of  yellow  ammonium  sulphide,  shake  with 
thoroughly,  warm  gently  without  boiling  and  allow  th 
to  digest  for  at  least  ten  minutes.     Filter  and  wash  the  ^ 
itate  with  a  warm,  dilute   solution  of  ammonium  sulphide. 
From  time  to  time  acidify  successive  portions  of  the  filtrate 
with  hydrochloric  acid  and,  when  this  produces  a  pure  white 
turbidity,  begin  to  wash  the  precipitate  with  cold  water,  con- 
tinuing the  washing  until  the  precipitate  no  longer  smells  of 
ammonium  sulphide. 

The  filtrate  {Aa)  contains  the  sulphides  of  arsenic,  antimony, 
tin,  (gold  and  platinum);  while  the  precipitate  {Bb)  consists  of 
sulphides  of  metals  of  the  fifth  group.     (Pass  to  §327). 

Examination  of  the  Ammonium  Sulphidb  Uolutiok  (Group  VI). 

326.  Add  hydrochloric  acid  to  filtrate  Aa  (r.  previous 
paragraph)  until  it  is  distinctly,  but  not  strongly  acid.     The 

_^ ^^ ^ 

>If  a  precipitate  forms  at  this  point,  it  probably  consists  of  a  basic  salt  of 
bismuth  or  antimony.  In  this  case,  filter,  wash  the  precipitate  and  test  it  for 
thoss  bases  (§§154,  179). 


,g  (NH.),S. 


*.»► 


78 


SrSTEMATIC  ANALTSIS. 


[»336 


precipitate  which  forms  will  consist  of  sulphides  of  Group  VI, 
mixed  with  free  sulphur.  Boil,  filter  and  wash  slightly. 
Transfer  the  precipitate  to  a  porcelain  dish,  add  an  excess  of 
concentrated  nitric  acid  and  boil  until  half  the  acid  is  boiled 
away.  Dilute  with  water  and  boil  again  for  one  minute- 
Globules  of  yellow  sulphur  may  remain  undissolved  and,  if  so, 

Tin  and     jj^gy  should  be  removed.*    If  a  white  precipitate  forms,  it  may 
mony.  ^.^j^gjgj  q£  metastannic  acid  or  melantimonic  acid*  (§§162,  165, 
179).     It  can  be  examined  jy  the  blow-pipe  (§384). 

Arsenic  '^^^  solution  may  contain  arsenic  in  the  form  of  arsenic 
acid,  H8ASO4,  and  a  little  antimony  as  antimonic  acid.  Test 
it  according  to  §170  or  §215  for  arsenic. 

Test  a  portion  of  the  insoluble  residue  for  tin  by  fusion  on 
charcoal  under  the  reducing  fiame  with  sodium  carbonate  and 
potassium  cyanide  mixture  (§165).  Digest  another  portion 
with  a  small  quantity  of  concentrated  hydrochloric  acid  in  a 
porcelain  dish.  Dilute  the  solution  with  three  times  its  bulk 
of  water  and  then,  no  matter  whether  the  residue  completely 

Antimony,  dissolves  or  not,  introduce  a  fragment  of  pure  zinc  and  a  piece 
of  platinum  foil  in  contact  with  one  another.  If  antimony  is 
present,  a  black  stain  will  appear  on  the  pL  mum  (§179). 
Pour  off  the  solution,  filtering  if  necessary,  and  .nix  it  with  a 
solution  of  mercuric  chloride.  If  the  latter  is  reduced,  giving 
a  white  or  gray  precipitate  of  mercurous  chloride  or  metallic 
mercury  (§125),  tin  is  present. 

If  it  is  desired  to  test  for  gold  and  platinum,  mix  a  portion 
of  the  precipitated  sulphides  {Bb.  §325)  with  sodium  carbon- 
ate and  nitrate,  and  fuse  in  a  porcelain  crucible.  The  noble 
metals  will  alone  be  reduced.  Boil  the  mixture  with  water, 
filter  and  wash.  Boil  the  residue  with  concentrated  hydro- 
chiloric  acid,.  The  portion  still  undissolved  is  gold  or  platinum. 
If  the  former,  it  can  be  fused  to  a  globule  in  the  oxidizing 


Tin. 


Gold  and 
platinuna. 


'  If  there  should  be  any  difficult}'  in  deciding  from  its  appearance  whether  the 
ur dissolved  residue  consists  entirely  of  sulphur,  heat  it  on  platinum  foil.  If 
It  first  fuses  and  theti  burns  away,  it  is  nothing  more  than  sulphur. 

»If  much  metantimonic  acid  is  present,  it  may  carry  down  with  it  a  part  or 
even  the  whole  of  the  arsenic  acid. 


*^ 


[§3^6 

Ihides  of  Group  VI, 
land  wash  slightly. 
3h,  add  an  excess  of 
|»lf  the  acid  is  boiled 
lin  for  one  minute 
idissolved  and,  if  so, 
:ipitate  forms,  it  may 
lie  acid»  (§§162,  165, 

jipe  (§3B4)- 
the  form  of  arsenic 

ntimonic  acid.     Test 

for  tin  by  fusion  on 

sodium  carbonate  and 

j>;e3t  another  portion 

ydrochloric  acid  in  a 

three  times  its  bulk 

;he  residue  completely 

:  pure  zinc  and  a  piece 

pther.     If  antimony  is 

the  pli  -num   (§i79). 

ary,  and  .nix  it  with  a 

tter  is  reduced,  giving 

us  chloride  or  metallic 

platinum,  mix  a  portion 
5)  with  sodium  carbon- 
i  crucible.  The  noble 
e  mixture  with  water, 
h  concentrated  hydro- 
ved  is  gold  or  platinum, 
lobule  in  the  oxidizing 

om  its  appearance  whether  the 
heat  it  on  platinum  foil.  If 
lore  than  sulphur. 

y  carry  down  with  it  a  part  or 


§319] 


DETECTION  OF  THE  BASES. 


IP 


BiRinuth. 


flame  on  charcoal.  Dissolve  the  metal  in  agua  r^^ /a  and,  after 
evaporating  most  of  the  aciu,  test  the  solution  for  gold  {§197) 
and  for  platinum  (§183). 

EX\MINATION    OF    THE    PRECIPITATED    SuLPHIDES    OF    MkTALS    OF 

,  .    ,         Group  V. 

327.  Transfer  the  precipitate  [Bb,  §325)  containing  AgjS, 
PbS,  CuS,  BijSg,  HgS,  CdS,  to  a  casserole,  pour  nitric  acid 
over  it  and  boil  for  some  time.  The  undissolved  residue,  if 
any,  consists  merely  of  sulphur,  if  it  is  yellow,  but,  if  dark 
colored,  it  may  contain  mercury.  In  the  latter  case  wash  it,  Mercury, 
dissolve  by  boiling  with  a  little  bromine  and  water  and  test 

for  mercury  according  to  §125. 

328.  The  solution  in  nitric  acid  is  to  be  cautiously  evapo- 
rated nearly  to  dryness,  then  freely  diluted  with  w;iter  and 
boiled.  The  appearance  of  a  w..'e  precipitate  indicates  bis- 
muth. Apply  confirmatory  test  (§§152-154).  Filter.  Add 
hydrochloric  acid  to  the  filtrate.  Any  silver  present  will  be 
precipitate'-l  as  a  silver  chlori  'e.  A  portion  of  the  lead  may 
also  be  thrown  down  as  lead  chloride.  Filter,  wash  the  pre- 
cipitate with  boiling  water,  and  test  it  for  silver  according  to 
§§ii6  and  118.  ■  :  '  i         T 

329.  To  the  filtrate  add  a  few  drops  of  dilute  sulphuric 
acid.  If  a  white  precipitate  forms,  it  consists  of  lead  sulphate. 
To  remove  the  lead,  add  a  con.siderable  excess  of  dilute  sul- 
phuric  acid.  Filter,  wash,  and  apply  confirmatory  tests  to  the 
precipitate.     (Compare  §§131  and  135).     , ;, 

The  filtrate  from  the  lead  sulphate,  or  the  solution  in  which 
sulphuric  acid  produced  no  precipitate,  will  contain  copper 
and  cadmium,  if  these  were  present.  Test  one  portion  for 
copper  by  the  addition  of  potasfium  fei  rocyanide,  (§140).  Copper, 
If  it  is  desired  to  test  also  for  cadmium,  proceed  with  a  second 
portion  as  follows.  Add  potassium  sulphocyanate  and  sodium 
sulphite  (or  sodium  thiosulphate).  Warm  the  solution,  but 
not  to  boiling,  for  five  minutes.  This  will  precipitate  all  the 
copper  as  cuprous  sulphocyanate,  Cu2(SCN)2,  leaving  the 
cadmium  in  solution.  Filter  and  treat  the  filtrate  with  HjS. 
A  yellow  precipitate  indicates  cadmium  (§156).  , 


Silver. 


»TItet™Ml*4-»^'V 


8o 


SrSTEMAT/C  ANALYSIS. 


[«33« 


Cadmium  may  also  be  detected  in  the  filtrate  from  the  lead 
sulphate  precirHate  by  treating  it  with  hydrogen  sulphide, 
then  boiling  .'  filtering.  The  cadmium  sulph'de  will  di»- 
Cudinlun).  solve  in  the  dilute  sulphuric  acid.  Filter  the  solution  from  the 
insoluble  CuS,  nearly  neutralize  with  ammonia  and  precipitate 
the  cadmium  with  hydrogen  sulphide. 

GROUPS   I,  II,  III   AND  IV. 

330,  The  filtrate,  {A)  from  the  hydrogen  sulphide  pre- 
cipitate, or  that  in  which  hydrogen  sulphide  produced  no 
precipitate  (§324),  is  to  be  differently  treated  according  to 
whether  phosphoric,  oxalic  or  boric  acids  are  present  or 
absent. 

It  should  therefore  next  be  tested  for  these  acids,  (§§203, 

Removal    204,  211,  212,  224  to  226).     If  oxalic  acid  alone  is  found,  add 

of  oxalates.  jQ  ^j^^.  golution  a  moderate  quantity  of  concentrated  sulphuric 

acid  and  evaporate  until  white  fumes  of  sulphuric  ai  id  begin 

to  appear.     This  treatment  destroys  the  oxalic  acid.    , 

Then  add  water  ^  and  proceed  with  the  solution  according 
to  the  following  section.  If  either  phosphoric  or  boric  (or 
eilicic)  acids  are  present;  follow  §338,  ei  se<j.,  otherwise  §331. 

SEPARATION   OF  GROUPS   III   AND   IV   FROM   GROUPS 

I   AND   II,   WHEN   PHOSPHORIC,  OXALIC   AND 

BORIC   ACIDS   ARE   ABSENT. 

I'rocipi-  33  ^  •     ^^^  ammonia  gradually  until  the  solution  is  neutral, 

tation  bv     then  add  ammonium  sulphide  in  slight  excess.     Warm  gently, 
ammoniuiTifjij.gr  jj„j  wash.     If  the  filtrate  has  a  tendency  to  run  through 

Bulpbide. 

ilf  complete  solution  does  not  take  place,  the  precipitate  consists  of  barium 
sulphate,  calcium  sulphate,  or  strontium  sulphdte,  or  a  mixture  of  these.  After 
filtration  and  washing,  this  precipitate  is  to  be  examined  for  Ba,  Sr,  and  Ca, 
{vide  §§344, 353)-  Enough  calcium  sulphate  will  remain  in  solution  to  be 
detected  in  the  regular  course  of  analysis.  If  the  precipitate  gives  dubious 
results  for  both  strontium  and  barium  by  the  ilame  test,  boil  it  with  sodium 
carbonate  solution,  filter  and  wash.  Treat  the  precipitate,  which  now,  probabl}-, 
consists  of  barium  sulphate  and  strontium  carbonate,  with  dilute  hydrochloric 
acid  and  filter  the  solution  from  the  undissolved  portion.  If  both  barium  and 
strontium  are  present,  the  solution  will  exhibit  the  flame  reaction  of  the  latter, 
whereas  the  precipitate  will  give  the  green  ha.ne  of  barium. 


t.«rf.*'.  ^/   «'-■  '..-jeAM*  *«i«%j:.'^..ia>»ftf*^««f'uJ4rff-;**Mft;W-.' 


'  'fjitlfm^wx  i<tt^!Vtit^t^it:gtie*MM 


W33' 


iltrate  from  the  lead 

hydrogen  sulphide, 

jm   sulph'de  will  dis- 

Ithe  solution  from  the 

lonia  and  precipitate 

IV. 

Irogen  sulphide  pre- 
ulphide   produced  no 

treated  according  to 
icids   are   present  or 

r  these  acids,  (§§203, 

:id  alone  is  found,  add 

oncentrated  sulphuric 

f  sulphuric  a<  id  begin 

oxalic  acid. 

the  solution  according 

losphoric  or  boric  (or 

ei  seq.,  otherwise  §33 1 . 

I   IV   FROM   GROUPS 
,  OXALIC   AND 
BSENT. 

1  the  solution  is  neutral, 
excess.  Warm  gently, 
jndency  to  run  through 

precipitate  consists  of  barium 
,  or  a  mixture  of  these.  After 
examined  for  Ba,  Sr,  and  Ca, 
ill  remain  in  solution  to  be 
the  precipitate  gives  dubious 
me  test,  boil  it  with  sodium 
cipitate,  which  now,  probablj-, 
late,  with  dilute  hydrochloric 
)ortion.  If  both  barium  and 
e  flame  reaction  of  the  latter, 
of  barium. 


*wit.va*ia.t°-wa^:^igw<mminiw 


DETECTION  OF  THE  BASES. 


brown,*  the  addition  of  ammonium  chloride  to  the  water  used 
for  washing  is  advisable.  The  filtrate  (C)  contains  bases  of 
Groups  I  and  II.     Pass  to  §342. 

332.  The  precipitate  (Z?)  may  contain  aluminium  hy- 
drate, chromium  hydrate,  manganese  sulphide,  ferrous  sulphide, 

zinc  sulphide,  nickel  sulphide,  cobalt  sulphide.     The  color  of  '"'«'""<""' 

,  .  .    .  ,        ,  ,  ,  ,   ,,        ,  -  from  color 

this  precipitate  should  be  carefully  observed.  ^i  ^^^  ^^^. 

If  it  is  white,  pale  green   or   flesh  -  colored,  nickel,  cobalt  cipitate, 
and  iron  must  be  absent.     In  this  case  omit  the  tests  for  these 
bases  and  pass  directly  to  §335.     Should  the  precipitate  be 
darker  in  color,  all  the  metals  of  Groups  III  and  IV  may  be 
present. 

Separation  of  Nickel  and  Cobalt  From  the  Other   Metals 

OF  Tins  Group. 

333.  Rinse  the  precipitate  D  (previous  section)  into  a 
small  flask,  add  dilute  hydrochloric  acid,  shake  thoroughly, 
and  allow  to  stand  in  the  cold  for  at  least  ten  minutes. 

If  the  precipitate  dissolves  entirely,  with  the  exception  of 
flakes  of  sulphur,  nickel  and  cobalt  are  absent.      (Pass  to 

§335)- 

If  there  is  an  undissolved  black  residue,  filter  and  wash. 

The  filtrate  (^)  is  to  be  examined  according  to  §335. 

Test  the  precipitate  in  the  borax  bead  in  the  oxidizing  flame  Njckei  and 
for  nickel  and  cobalt  (§§  9,  78,  84).  cobalt  In 

Should  the  precipitate  be  too  small  in  quantity  to  remove  *^*  *^'''"' 
from  the  filter  paper,  tear  off  the  apex  of  the  filter  with  the 
precipitate,  wrap  it,  while  still  moist,  around  the  borax  bead 
and  expose  to  the  oxidizing  flame. 

The  filter  paper  vyiH  rapidly  burn  away  and  the  precipitate 
will  dissolve  in  the  borax. 

If  the  bead  is  blue  in  the  oxidizing  and  in  the  reducing 
flame,  cobalt  is  present  (§78),  but  if  brown  in  the  oxidizing 
flame   and  colorless  to    gray  in  the  reducing   flame,   nickel 

(§84)- 
If  on  the  contrary  the  bead  is  clear  blue  in  the  reducitig 


bead. 


> This  Is  only  likely  to  occur  when  nickel  Is  present. 


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Photographic 

Sciences 

Corporation 


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(716)  872-4503 


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CIHM/ICMH 

Microfiche 

Series. 


CIHM/ICIVIH 
Collection  de 
microfiches. 


Canadian  Instituta  for  Historical  Microreproductions  /  Institut  Canadian  de  microraproductiont  histo'iquas 


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5  rs  TEMA  TIC  ANAL  rSIS. 


(§336 


Precipi- 
tation of 
cobalt 
with 
KNO,. 


Hydrates 
of  Fe,  Mn 
and  Cr. 


Iron. 
Manganese 


Chromium 


flame  but  dirty  blue  in  the  oxidizing  flame,  both  cobalt  and 
nickel  may  be  suspected. 

334*  Often  when  both  nickel  and  cobalt  are  present, 
they  can  not  be  distinguished  from  one  another  by  their 
behaviour  in  the  borax  bead.  In  such  cases  they  may  be 
separated  by  the  following  process. 

Dissolve  the  precipitate  (Z?,  §332)  in  a  small  quantity  of 
hot,  concentrated  hydrochloric  acid.  Add  potassium  acetate 
and  potassium  nitrite,  KNO2,  in  excess,  and  allow  to  stand 
in  a  warm  place  for  some  time.  Cobalt  appears  as  a  yellow 
precipitate  of  potassium  cobaltic  nitrite,  K8Co(N02)6,  (§80). 
Filter,  evaporate  the  filtrate  to  dryness  and  test  tiie  residue  by 
the  borax  bead,  in  the  oxidizing  flame,  for  nickel  (§84). 

335.  The  filtrate  {E,  §333)  from  the  sulphides  of  nickel 
and  cobalt  is  to  be  boiled  to  expel  H2S.  Add  bromine- water 
in  slight  excess  and  then  sodium  hydrate  in  considerable  excess. 
Boil  in  a  porcelain  dish  for  one  minute.  The  precipitate  {F), 
if  any,  contains  the  iron,  manganese  and  chromium.*  Dilute, 
and  filter.     The  filtrate  ( G)  contains  zinc  and  aluminium. 

336.  Examine  the  precipitate  {F)  for  iron,  manganese 
and  chromium  [and  also  for  zinc,  if  chromium  is  found')  as 
follows : 

Dissolve  a  small  portion  in  dilute  hydrochloric  acid  and  test 
it  with  KSCN  or  K4Fe(CN)6  for  iron  (§§97,  98). 

Test  another  portion  for  manganese  in  the  borax  bead  or 
sodium  carbonate  bead  (§§106,  107). 

Mix  the  greater  portion  of  the  precipitate  with  sodium  car- 
bonate and  sodium  nitrate  (see§7i,  «).  Fuse  on  platinum 
foil  for  one  minute.  Dissolve  the  melt  in  water  and,  if  the 
solution  is  green,  boil  it  with  a  few  drops  of  alcohol  and  filter. 
If  the  filtrate  is  yellow,  chromium  is  present.  Acidify  the 
filtrate  with  acetic  acid.  If  yellow,  divide  it  into  two  parts. 
To  one  part  add  lead  acetate,  as  confirmatory  test  for  chro- 
mium (§71,  «).  To  the  other  part  add  potassium  fenocy- 
anide.     A  white  precipitate  indicates  zinc  (§112). 

>If  much  chromium  is  present,  this  precipitate  may  also  contain  a  part  or 
the  whole  of  the  zinc. 


^iimSi,. 


.^  "        (§336 

Lme,  both  cobalt  and 

cobalt  are    present, 

lie   another   by  their 

cases  they  may  be 

a  small  quantity  of 
:d  potassium  acetate 

and  allow  to  stand 
appears  as  a  yellow 
K8Co(NOa)6,  (§80). 
id  test  the  residue  by 
r  nickel  (§84). 
e  sulphides  of  nickel 

Add  bromine- water 

n  considerable  excess. 

The  precipitate  {F), 

chromium.*     Dilute, 

c  and  aluminium. 

for  iron,  manganese 
iromium  is  found)  as 

ochloric  acid  and  test 

§§97,  98). 

in  the  borax  bead  or 

tate  with  sodium  car- 
Fuse  on  platinum 
in  water  and,  if  the 
3  of  alcohol  and  filter, 
present.  Acidify  the 
ide  it  into  two  parts, 
natory  test  for  chro- 
d  potassium  ferrocy- 
:  (§112). 

may  also  contain  a  part  or 


§339] 


DETECTION  OF  THE  BASES. 


337.  Examine  filtrate  G  (§335)  for  aluminium  and  zinc 
as   follows.      Acidify   slightly   with   hydrochloric   acid;    add 
ammonia  in  considerable  excess  (§64).     Let  it  stand  for  ten  Aluminium, 
minutes.     The  formation  of  a  white  precipitate  {H)  indicates     •         / 
aluminium.     Filter  and  wash.     Test  the  filtrate  for  zinc  with  zinc, 
ammonium  sulphide  (§111).     A  white  precipitate  indicates 
zinc*  :',:^;  i.v.,.-;';  •', 

Transfer  a  part,  or  the  whole,  of  the  precipitate  [H)  to  a 
charcoal  stick;  ignite  in  the  oxidizing  flame  and  test  with 
cobalt  nitrate  for  aluminium*  (§64). 

EXAMINATION   OF   GROUPS   III   AND   IV,  IN   PRESENCE 
OF   PHOSPHATES,   BORATES  OR    SILICATES. 

■A  V   . 

338.  When,  of  these  acids,  silicic  acid  alone  is  present,  it 
may  be  removed  by  the  processes  described  in  §§228  or  231,  ^*  ""**' 
and  the  residual  solution  then  analyzed  in  the  usual  way.' 

339.  Phosphoric  or  boric  acids  having  been  found,  pro-     O- '  ;<-  ■ 
ceed  as  follows  witlj  the  solution  {^A,  §324). 

Boil  to  expel  hydrogen  sulphide,  add  bromine-water  in  slight  Removal 
excess,  and  boil  to  expel  the  excess.     Test  a  small  sample  of  °*  P''"*" 
the  solution  for  iron  (§97)-     Add  ferric  chloride  and  then  ^"arg"" 
ammonia  in  excess.     The  precipitate  should  be  brown.     If  it  1' 

is  white,  this  shows  that  not  enough  ferric  chloride  has  been     , 
added  to  combine  with  all  the  phosphoric  acid.     Add  an  addi- 
tional amount   of  ferric   chloride  in   this  case,  then  acidify 
cautiously  with  acetic  acid.     Boil  for  three  minutes,  filter  and  ;    j"  .     ; 
wash.     The  precipitate  (/)  contains  the  phosphoric  acid  (or 
boric  acid)  in  combination  with  iron,  and  all  the   rest  of  the  ^**'*=       ^L 
iron,  the  chromium  and  the  aluminium  as  basic  acetates.   Pass  *ngth<xi 
to  §§340,  341-  . 

»Confirmatorj  test,  §109. 

•This  confirmator/  test  for  aluminium  should  never  be  omitted. 

*If  the  solution  contains  fluorides,  it  may  be  treated  as  described  in  the  fol- 
lowing section.  The  process  there  described  removes  the  hydrofluoric  acid  \i\ 
the  form  of  basic  ferric  fluoride.  Or,  the  solution  may  be  evaporated  to  dry- 
ness and  then  heated  to  a  high  temperature  with  an  excess  of  concentrated  sul- 
phuric acid  until  the  HF  is  all  expelled.  Since  solutions  containing  fluorides 
can  not  be  analyzed  in  glass  vecsels,  it  is  seldom  necessary  in  qualitative  anal-  ,'•  •  ?  . 
yses  for  practice  to  remove  this  acid. 


"> 


84 


SYSTEMATIC  ANALYSIS. 


[«344 


^ ! 
i'  : 


'\  I 


ll 


340-  The  filtrate  (7)  contains  the  remaining  bases  of 
Groups  IV  and  those  of  II  and  i.  Proceed  with  the  examina- 
tion of  this  filtrate  (  50  in  the  usual  way,  beginning  at  §3;»i, 
but  omitting  all  that  relates  to  the  tests  for  iron. 

34 1 •  Transfer  the  precipitate  (/,  §339)  to  a  porcelain 
of  Ai  and  ^"^^y  add  sodium  hydrate,  boil  and  filter.  Test  the  filtrate  for 
Cr.  aluminium  by  §337  and  the  precipitate  for  chromium  by  fusion 

with  sodium  carbonate  and  nitrate.,  etc.     (§71,  «)• 

SEPARATION   OF  THE  SECOND  GROUP    FROM   THE    FIRST. 

342.  Boil  the  solution  (filtrate  C,  §331)  from  which 
bases  of  the  higher  groups  have  been  removed,  until  it  no 
longer  smells  of  ammonium  sulphide;  add  ammonium  chloride 
tatlon  by  ^nd  then  ammonium  carbonate  in  slight  excess.  Warm  gently, 
(NH«)jCO».  but  not  to  boiling.  If  a  precipitate  (A")  forms,  it  m'  j  contain 
the  carbonates  of  calcium,  barium  and  strontium.  (Pass  to 
§344  or  345).     P'ilter  and  wash. 

343*  The  filtrate  (Z)  contains  magnesium,  sodium  and 
potassium,  if  these  are  present.  Divide  it  into  two  parts. 
Magnesium.  Test  one  part  with  sodium  phosphate  and  ammonia  according 
to  §61,  for  magnesium.  Only  when  a  crystalline  precipitate 
forms  at  this  point,  can  you  safely  conclude  that  magnesium  is 
present. 

Test  the  other  portion  of  filtrate  (Z)  for  sodium  and  potas- 
sium (§346)- 

The  Separation  and  Detection  of  Barium,  Strontium  and 

Calcium. 

344.     Dissolve  the  precipitate  (A")  in  the  least  possible 

quantity  of  dilute,  hot  hydrochloric  acid.     Dip  a  clean  platinum 

wire  in  the  solution  obtained  and  hold  it  in  the  Bunsen  flame. 

An  orange  color  indicates  calcium  (§43) ;  scarlet,  strontium 

(§47);  or  green,  barium  (§51). 

Divide  this  solution  {^M')  into  two  parts.     To  one  part  add 

Precipi-     ^  solution  of  calcium  sulphate.     If  a  precipitate  forms  at  once, 

CaSO  ^   barium  is  present.     If  it  forms  only  after  standing  for  some 

time,  strontium  is  indicated.     In  either  case  filter,  wash  and 

apply  confirmatory  flame  test  to  the  precipitate.     Should  no 


>. 


--■Iff  'iiii'WJMMIi 


V •...:'. :-■:..  ..:;  [§344 

remaining  bases  of 
led  with  the  examina- 
U  beginning  at  §3:;i, 
l)r  iron. 
R339)  to  a  porcelain 
Test  the  filtrate  for 
br  chromium  by  fusion 
(§71,  a). 

FROM   THE    FIRST. 

§331)   from    which 

removed,  until  it  no 

Id  ammonium  chloride 

xcess.     Warm  gently, 

forms,  it  m-  y  contain 

strontium.     (Pass  to 

ignesium,  sodium  and 
ide  it  into  two  parts. 
Ind  ammonia  according 
;  crystalline  precipitate 
lude  that  magnesium  is 

for  sodium  and  potas- 


RiUM,  Strontium  and 

)  in  the  least  possible 

Dip  a  clean  platinum 

it  in  the  Bunsen  flame. 

if 3);  scarlet,  strontium 

rts.  To  one  part  add 
icipitate  forms  at  once, 
ter  standing  for  some 
r  case  filter,  wash  and 
recipitate.     Should  no 


Calcium. 


Strontium. 


DETECTION  OF  THE  BASES. 

precipitate  form,  barium  and  strontium  are  both  absent.  In 
this  case,  test  the  second  portion  of  solution  M  for  calcium,  as 
given  below. 

If  the  examination  above  has  shown  the  presence  of  barium 
or  strontium,  add  dilute  sulphuric  acid  to  the  second  portion 
of  the  solution  (M)  until  no  further  precipitate  [Mm)  forms. 
Filter  and  wash.  Neutralize  the  filtrate  with  ammonia,  then 
add  ammonium  oxalate.  The  formation  of  a  precipitate  indi- 
cates caHum,  (§46).     Apply  confirmatory  flame  test. 

The  pi  ecipitate  Mm,  which  may  consist  of  a  mixture  of  the 
sulphates  of  bariuiii  and  strontium  or  of  either  of  these  salts  '  ' 
alone,  should  be  examined  for  both  metals  by  the  method  Barium, 
described  in  the  last  part  of  §353.  It  is  necessary  to  do  this, 
even  when  the  flame  test  seems  to  show  that  only  one  of  the 
metals  is  present,  for  the  reason  that  either  of  the  two  bases  if 
present  in  large  excess  may  obscure  the  flame  reaction  of  the 
other. 

i-:'-'"-' . 

Second  Method  for  the  Separation  and  Detection  of  Calcium, 
Strontium  and  Barium. 

345*  The  method  just  described  does  not  always  give,  in 
inexperienced  hands,  satisfactory  results,  when  strontium  and  ' 

barium  are  both  present.     The  following  process  may  be  ; 
used  instead. 

Neutralize  the  hvdrochloric  acid  solution  of  the  carbonates 
{M,  §344)  with  ammonia,  acidify  slightly  with  acetic  acid  and  '  . 
add  potassium  pyrochromate  in  excess.     The  appearance  of  a  Removal 
pale  yellow  precipitate  (TV)  ^  indicates  barium.     Filter  and  o*  barium 
test  the  filtrate  ( G)  with  a  drop  of  dilute  sulphuric  acid  for  **  ^        * 
strontium  (§48).    |f  a  white  precipitate  forms,  it  consists  of 
strontium  sulphate.     In  this  case,  add  sulphuric  acid  drop  by 
drop  until  no  further  precipitate  forms,  filter,  neutralize  the 
filtrate  with  ammonia  and  add  ammonium   oxalate.      The 
appearance  of  a  white  precipitate,  of  calcium  oxalate,  indicates 
calcium  (§46).     Apply  confirmatory  ^est. 


'The  precipitate  N,  consieting  of  barium  ciiromate,  may  be  moistened  with 
HCl  and  tested  on  a  platinum  wire  in  the  flame  (§51). 


'    t 

f 


— , 


».T 


1 1 


¥■ 


V. 


V. 


86 


SrSTEMATIC  ANALTSrS. 


t§349 


''  Detbction  of  the  Bases  of  Group  I. 

346-     '^^*^  solution  (Z,  §343)  may  be  directly  tested  for 
and  pota»-  sodium  and  potassium  by  the  flame  test  or  by  either  of  the 
reactions  given  in  §§30,  33,  34  and  35. 

347.  Ammonium  salts  must  be  tested  for  in  a  portion  of 
the  original  solution.  To  this  end,  add  potassium  hydrate  or 
sodium  hydrate  in  excess  and  warm  the  solution.  If  the 
escaping  vapours  smell  of  ammonia  and  exhibit  an  alkaline 
reaction,  an  ammonium  compound  is  present  (§38). 


slum. 


Ammo- 
nium. 


EXAMINATION    OF  INSOLUBLE  SUBSTANCES. 


'.  * 


'I    i 


■!! 


.*}    ' 


Solution 
of  non- 
metallic 
solids. 


348.  If  the  substance  under  tvamination  is  a  solid,  it  must 
be  brought  into  solution  *or  analysis.  It  should  be  dissolved 
in  water  if  possible.  If  insoluble  in  water  and  non-metallic,  1 
treat  it  with  dilute  hydrochloric  acid.  If  insoluble  even  on 
warming,  heat  it  with  dilute  nitric  acid.  If  insoluble  in  this 
menstruum  also,  try  a</ua  regia.^  If  it  dissolves,  dilute  the 
solution  with  water  and  boil  to  expel  chlorine.  If  the  sub- 
stance is  dissolved  by  either  of  these  mode.*'  of  treatment  the 
solution  may  be  analyzed  by  the  methods  already  given. 

349.  •  If  the  substance  is  insoluble  in  hydrochloric  acid, 
nitric  acid  or  aqua  regia,  it  is  probably  one  of  the  bodies 
enumerated  in  the  following  list : 


Sulphur. 

Carbon. 

Barium  Sulphate. 

Strontium  Sulphate. 

Lead  Sulphate. 

Aluminium  Oxide. 

Chromium  Oxide. 


Silver  Chloride. 

Silver  Bromide. 

Silver  Iodide. 

Stannic  Oxide. 

Silica. 

Many  SilicatesfT 

Compound  Cyanides. 


Some  clue  as  to  the  nature  of  the  substance  will  have  been 
obtained  in  the  preliminary  examination,  and  the  methods 
given  below  will  be  found  useful  for  its  complete  identification. 

m  it  is  metallic,  follow  §§382,  383,  or  Table  I,  p.  104. 
*Four  pa-.ts  strong  hydrochloric,  one  part  strong  nitric  acids. 


'    '■ 

•  -^.^  ■  1   -'.„■■' 

•' 

;•;  ■ 

"';.■■■ 

:',i: 

',!' 

n. 

.  .'j  *'  f  * , 

■i^-  ..'-.:■■.■■ 

■iMi 

MHM 

■.-y 

■  -rfilWIWimilBWHTM'triliHIWIMMW 


»  w. 


[§349 


SROUP    I. 


directly  tested  for 
lor  by  either  of  the 

Id  for  in  a  portion  of 
lotassium  hydrate  or 
|he  solution.  If  the 
exhibit  an  alkaline 
[sent  (§38). 

SUBSTANCES. 

ation  is  a  solid,  it  must 
It  should  be  dissolved 
ter  and  non-metallic,' 
If  insoluble  even  on 
If  insoluble  in  this 
it  dissolves,  dilute  the 
chlorine.     If  the  sub- 
codes of  treatment  the 
ds  already  given. 
;  in  hydrochloric  acid, 
bly  one  of  the  bodies 

'hloride. 
romide. 
jdide. 
O.xide. 

ilicatesr 

nd  Cyanides. 

bstance  will  have  been 

ion,   and   the  methods 

complete  identification. 


1. 104. 

I  nitric  acids. 


[§353 


INSOLUBLE  COMPOUNDS. 


Combusti- 
bility of 


350.  Sulphur.  Crystalline  sulphur,  although  soluble  on 
continued  boiling  with  nitric  acid,  forming  sulphuric  acid,  may 
be  met  with  here.  If  heated  on  platinum  foil,  it  bums  with  a 
characteristic  blue  flame,  without  leaving  any  residue.  If 
boiled  with  sodium  hydrate  and  a  silver  coin,  the  latter  will  be 
blackened. 

351.  Carbon.     Carbon   in   some  of   its  forms,  as  gas- 
retort  carbon  or  as  graphite,  is  almost  insoluble  in  boilinp' 
nitric  acid.     Its  combustibility  by  prolonged  heating  in  the  carbon. 
oxidizing  flame  and  its  physical  properties  serve  for  its  identi- 
fication. 

In  case  much  carbon  is  intimately  mixed  with  relatively 
small  quantities  of  other  substances,  as  in  the  carbon  sticks 
employed  in  the  production  of  the  electric  arc  light,  the  carbon 
hinders  the  solubility  in  acids  of  other  constituents.     The  latter  .  ;■  • 

must,  accordingly,  be  detected  in  the  ash,  after  burning 
away  the  carbon.  To  this  end,  pulverize  the  material  finely,  q£  ^g^.*  * 
spread  it  in  a  thin  layer  over  a  sheet  of  platinum  and  heat  the 
latter  to  incandescence  with  the  Bunsen  flame.  The  carbon 
will  slowly  be  consumed.  The  ash  is  to  be  analyzed  as 
directed  for  silicates,  §357. 

352.  Barium  Sulphate.  Barium  sulphate  gives  a 
green  flame  coloration,  and  the  sulphur  reaction  when  fused 
on  charcoal  with  sodium  carbonate  (§193). 

In  mixtures  of  lead  sulphate   with  barium   sulphate   the  „ 

,  ,  ,  .  ,  ,  .  Separation 

former  may  be  separated  by  takmg  advantage  of  its  solubility  of  PbSOi 
in  a  solution  of  ammonium  acetate  in  strong  ammonia.     The  from  BaSOi 
barium  sulphate  will  remain  undissolved  and  may  then  be 
readily  recognized  by  the  flame  reaction,  etc.,  which  would 
have  been  difficult  before  the  removal  of  the  lead  sulphate. 

353.  Strontium  Sulphate  gives  the  strontium  flame, 
and  the  sulphur  reaction.  If  fused  with  sodium  carbonate 
on  platinum  foU,  it  is  decontposed  as  follows : 

SrSOi  +  NaaCOs  =  SrCOg  +  NajSO* 
Boil  the  melt  with  water,  filter;    test  the  filtrate  for  sul- 
phuric acid  (§307).     Dissolve  the  precipitate  in  dilute  nitric 
acid  and  test  for  strontium  (§§47,  48). 


* 
^ 


4 

'-it 

I 


\4i 


"1 


^j&\  />r 


WM 


'i  1 


11 


1*1 ! 


Si.  I 

(I 


Si 
1? 


$ 


P 


SrSTEMAT/C  ANALrSIS. 


M3S6 


Mixtures 
of  BaSO, 
and  SrSOi. 


If  the  subitance  consists  of  a  mixture  of  strontium  sulphate 
with  barium  sulphate,  both  bases  may  be  detected  by  the 
following  procedure. 

Boil  the  mixture  with  an  excess  of  a  dilute  solution  of 
sodium  carbonate.  This  converts  most  of  the  strontium  sul- 
phate into  strontium  carbonate,  but  has  little  effect  upon  the 
barium  sulphate.  Filter  the  solution  and  wash  the  precipitate 
until  no  longer  alkaline.  Treat  the  precipitate  with  warm, 
hydrochloric  acid,  filter,  and  wash.  The  solution  will  contain 
the  strontium  and  is  to  be  tested  for  it  by  the  flame  reaction, 
while  the  barium  may  be  detected  in  the  same  way  in  the 
undissolved  portion  of  the  precipitate. 

354.  Lead  Sulphate  turns  black  on  treatment  with 
ammonium  sulphide.  It  affords  globules  of  lead  when  fused 
on  charcoal.  It  may  be  brought  into  solution  in  the  same  way 
as  strontium  sulphate,  §353.     (Compare  §352). 

355.  Silver  Chloride,  Bromide  and  Iodide  may  be 
Reduction  recognized  by  their  properties  as  given  in  §§ii6,  117,  118. 

If  it  is  suspected  that  the  insoluble  substance  may  contain 
two  of  these  silver  salts,  or  all  three,  mix  it  with  its  own 
weight  of  dry  sodium  carbonate  and  fuse  in  a  porcelain  cruci- 
ble. Extract  the  residue  with  water  and  examine  the  solution 
for  iodides,  bromides  and  chlorides  (§317). 

Another  method  of  separating  the  haloids  from  their  insolu- 
ble compounds  with  silver,  is  to  digest  the  substance,  which 
perhaps  contains  AgCl,  AgBr  and  Agl,  with  fresh  ammonium 
sulphide  for  an  hour  or  two.  Finally,  boil  and  filter.  The 
precipitate  contains  the  silver  as  sulphide,  while  the  haloids  are 
present  in  the  form  of  ammonium  salts  in  the  filtrate,  where 
they  may  easily  be  detected  (/.  c). 

356.  Stannic  Oxide,  or  Mktastannic  Acid,  (v.  §§162 
to  165).  It  may  be  brought  into  solution  as  potassium  stan- 
nate,  KaSnOg,  by  fusion  with  potassium  carbonate  and  treat- 
ment with  water. 

If  metastannic  acid  is  mixed  with  the  insoluble  compounds 
mentioned  above  (§§351  to  355),  it  may  be  isolated  by  taking 
advantage   of    its  solubility  in  yellow  ammonium   sulphide. 


of 

insoluble 
silver  salts. 


i" 


MMHMMfMtfe.- ■. 


[ 


[|3S6 

strontium  sulphate 
)e  detected  by  the 

dilute  solution  of 
|£  the  strontium  sul- 
ttle  effect  upon  the 
wash  the  precipitate 
cipitate  with  warm, 
solution  will  contain 
the  flame  reaction, 
the  same  way  in  the 

on  treatm'^nt  with 
of  lead  when  fused 
ution  in  the  same  way 
§352). 
AND  Iodide  may  be 
in  §§ii6,  117,  118. 
abstance  may  contain 
,  mix  it  with  its  own 
se  in  a  porcelain  cruci- 
id  examine  the  solution 

loids  from  their  insolu- 
t  the  substance,  which 
,  with  fresh  ammonium 
,  boil  and  filter.  The 
le,  while  the  haloids  are 
s  in  the  filtrate,  where 

VNNic  Acid,  {v.  §§162 
ion  as  potassium  stan- 
n  carbonate  and  treat- 

ie  insoluble  compounds 
y  be  isolated  by  taking 
'  ammonium   sulphide. 


^mm* 


§3571 


INSOLUBLE  COMPOUNDS. 


89 


Digest  it  over  night  with  a  considerable  excess  of  the  reagent 
named,  then  filter  and  wash.  Sometimes  several  repetitionH 
of  the  digestion  will  be  requisite  to  entire*/  remove  the  tin. 
The  filtrate  will  contain  the  tin  as  ammonium  sulphostannate,  ,: 
and  acidification  with  hydrochloric  acid  will  precipitate  it  as 
stannic  sulphide  (§§160,  165). 

357.    Silica.     (See  §§228,  230  and  331).     Silicates  may 
be  recognized  by  fusion  with  the  microcosmic  salt  bead,  §232.  AnaiynU 
Silica  and  m£.ny  of  its  compounds,  when  finely  pulverized  and  ofsilicatci. 
heated  before  the  blowpipe,  after  moistening  with  cobalt  nitrate 
solution,  become  falc  blue.     (Cf.  §64). 

In  order  to  prepare  a  silicate  for  analysis,  it  should  be  finely 
pulverized  and  mixed  with  five  times  its  weight  of  dry  sodium 
carbonate  and  about  one-tenth  its  weight  of  sodium  nitrate, 
and  the  mixture  fused  thoroughly  on  platinum  foil  or  in  a    , 
platinum  crucible.     Boil  the  fused  mass  with  water  until  it  is  ,' . 
softened.      Acidify  strongly  with  hydrochloric  acid,  evaporate 
the  solution  to  dryness  and  treat  as  directed  in  §228,  to  sepa-         ,-     ' 
rate  the   silicic   acid.      The   filtered  solution   may  then   be 
analyzed  according  to  the  general  methods,  bearing  in  mind 
that  it  cannot  be  used  for  the  detection  of  sodium  and  potas- 
sium. 

The  latter  may  sometimes  be  detected  by  moistening  the         -     ■' 
finely  powdered  silicate  with  sulphuric  acid  and  introducing 
the  mixture  on  the  platinum  wire  into  the  flame,  when  the        ^ 
characteristic  yellow  of  sodium  or  violet  of  potassium  may  be 
observed. 

Another  method  of  preparing  silicates  for  analysis,  and  a 
better  one  than  the  first  described,  in  so  far  as  it  permits  the  Detection 
detection  of  sodium  and  potassium  with  certainty,  is  dependent  o'  alkalies 
upon  the  expulsion  of  the  silica  in  the  form  of  silicon  fluoride,  '"  *"*<=ate8. 
SiFi  (§231).     Pulverize  the  silicate  (about  \  gram)   finely 
and  digest  with  hydrofluoric  acid  in  a  platinum  dish  until  com- 
pletely decomposed.    Then  add  about  i  c.c.  of  concentrated 
stxlphuric  acid  and  heat  until  the  water,  hydrofluoric  acid  and 
silicon  fluoride  are  expelled.    This  point  will  be  indicated  by 
the  evolution  of  dense,  white,  suffocating  vapour  of  sulphuric 
acid.    When  cold,  dilute  with  water.    A  white  precipitate       '   '    ' 


I 


% 

i 


■-Tl 

I 
1 


mwmmmmmmmm 


fp 


m^ 


tf'.V 


90 


SYSTEMATIC  ANALYSIS. 


11360 


„;  I 

i 


^N 


may  consist  of  barium  sulphate  (*5352),  strontium  sulphate 
(S353)»  calcium  sulphate  (§44),  lead  sulphate  (§4^354,  i3*)»  o"" 
metastannic  acid  (^162,  356).  If  a  precipitate  forms,  filter 
and  wash  thoroHghly.  The  filtrate  may  be  analyzed  in  the 
regular  way,  omitting,  of  course,  the  tests  for  sulphuric  acid, 
barium,  strontium  and  lead. 

358.  Compound  Cyanidks.  If  an  insoluble,  compound 
Conversion  cyanide  be  boiled  for  some  time  with  concentrated  sulphunc 
of  cyanide*  acid,  the  nitrogen  of  the  cyanide  will  be  converted  into  ammo- 

"'°       '■    nium  sulphate  and  in  the  solution  the  amn  jnia  may  be  detect- 
ed by  §38  or  §40,  and  the  bases  by  the  usual  methods.^ 

359.  Aluminium  Oxide  and  Chromium  Oxide,  after 
prolonged  ignition,  or  when  occurring  as  minerals,  are  often 
totally  insoluble  in  the  ordinary  acids.  They  may  be  rendered 
soluble,  after  finely  pulverizing,  by  prolonged  fusion  at  a  dull 
red  heat  with  acid  potassium  sulphate,  or  by  fusion  with  the 
oxidizing  flux  mentioned  in  §71,  p.  21.  The  latter  treatment 
will  convert  the  alumina  into  sodium  aluminate  and  the  chro- 
mium oxide  into  sodium  chromate.  The  alumina  can  be 
precipitated  from  the  solution  after  filtration  by  ^^,  and  its 
prc'sence  confirmed  by  §64.  The  filtrate  from  the  aluminium 
hydrate  can  be  used  for  the  detection  of  the  chromic  acid. 

REMOVAL  OF  ORGANIC  MATTER. 

360.  A  substance  containing  organic  matter  is  usually 
blackened  by  the  application  of  heat;  moisture  and  empyreu- 
matic  vapours  being  frequently  evolved  at  the  same  time. 
When  organic  matter  is  found,  it  must  be  removed  before 
proceeding  to  the  analysis,  because  such  matter  interferes  with 
many  of  the  reactions  of  bases  and  acids.  In>  case  the  bases 
and  acids  to  be  tested  for  are  those  which  will  stand  a  red 
heat  without  volatilization  or  decomposition,  the  best  way  to 
remove  organic  matter  is  to  burn  it  off  by  ignition  of  the 
substance  on  platinum  foil  or  in  a  crucible.     Otherwise  the 


Combus- 
tion. 


|! 


1 

4 

■Ttiis  mode  of  examination  does  not  show  wMat  compound  cyanides  are 
present,  thnt  being  a  difficult  problem,  the  full  discussion  of  which  woulU 
exceed  the  limits  of  this  work. 


.•lllilWIIIIM-lllWIMiUMniB  ■  r- 


«■•> 


rt36o 

strontium  sulphate 

[ate  (§4^354, 131),  or 

pcipitate  forms,  filter 

be  analyzed  in  the 

Is  for  sulphuric  acid, 

insoluble,  compound 

ncentrated  8ulphu.4c 

onverted  into  ammo- 

jnia  may  be  detect- 

sual  methods.* 

oMiUM   Oxide,  after 

IS  minerals,  are  often 

hey  may  be  rendered 

nged  fusion  at  a  dull 

or  by  fusion  with  the 

The  latter  treatment 

minate  and  the  chro- 

The  alumina  can   be 

tration  by  ^66,  and  its 

te  from  the  aluminium 

the  chromic  acid. 

MATTER. 

nic  matter  is  usually 
noisture  and  empyreu- 
^d  at  the  same  time, 
st  be  removed  before 
I  matter  interferes  with 
Is.  In-  case  the  bases 
Arhich  will  stand  a  red 
ition,  the  best  way  to 
off  by  ignition  of  the 
icible.     Otherwise  the 


Aat  compound  c,vanides  are 
discussion  of  which  woulU 


KBMOVAL   OF  ORGANIC  MATTER 


organic  substances  may  be  oxidized  and  destroyed  by  the  fol- 
lowing method,  which  is  well  suited  for  the  detection  o! 
arsenic,  lead,  mercury  and  other  inorganic  poisons  in  articles 
of  food,  parts  of  the  human  body,  et 

Mix  the  material  with  an  equal  volume  of  concentrated 
nitric  acid,  warm  gently  and  throw  into  the  mixture,  while 
warm,  .1.  little  powdereil  potassium  chlorate.  Continue  the 
heating  for  some  time,  adding  occasionally  potassium  chlorate 
in  small  quantities.  Evaporate  most  of  the  nitric  acid,  dilute 
with  witer  and  analyze  the  solution  in  the  usual  way.  It 
must  b<!  remembered  that  this  treatment  converts  all  sulphur 
compounds  present  into  sulphuric  acid  and,  in  general,  most  of 
the  elements  into  their  highest  state  of  oxidation.  Iodine  and 
bromine  are  expelled,  in  part  at  least,  with  the  escaping 
vapours.  These  elements  and  chlorine  may  be  detected  by 
heating  the  original  substance  with  concentrated  sulphuric 
acid  '.,nd  passing  the  escaping  vapour;  into  water,  in  which 
the  hydroch!o*ic,  hydrobromic  or  hydriodic  acid  will  dissolve 
and  in  which  they  may  be  detected  by  the  usual  methods;  the 
sulphurous  acid,  evolved  by  the  action  of  the  sulphuric  acid 
on  organic  substances,  sufficing  to  reduce  any  iodine  which 
might  be  liberated,  back  again  to  the  form  o   hydriodic  acid. 

Any  treatment  which  would  destroy  organic  matters  would 
also  decompose  hydrocyanic  acid  (or  its  salts),  if  present.  To 
detect  this  acid,  therefore,  in  mixtures  of  the  kind  under  con- 
sideration, advantage  is  to  be  taken  of  its  volatility.  About 
100  grams  of  the  material  is  to  be  acidified  with  acetic  acid, 
introduced  into  a  flask  or  retort  connected  to  a  condenser,  and 
then  subjected  to  slow  distillation  until  one-fifth  of  the  liquid 
part  of  the  substance  has  collected  in  the  receiver.  Hydro- 
cyanic acid,  if  present,  will  be  found  in  the  distillate  by  either 
of  the  tests  given  in  previous  paragraphs  (§§282-284). 


Oxidation 
of  organic 
matter. 


Detection 
of  "prussic 
acid." 


I 


a- 


":;i 


1 


\m**t^*t%t  .-*.■*-,**»!%•" 


■HPWiilP 


mmm 


P. 

if 


f\ 


5. ! 

The 

conttitu- 
ents  of 
poUble 
waters. 

'■■'  ) 

Saline 

,'1     t 

III 

in  well- 
water. 

# 

&4 


•  r  v-,7',  .■■ 
..■■.■■  .,  V'.- 


CHAPTER  V. 


SPECIAL   PART. 


ANALYSIS  OF  POTABLE  WATER. 

361.  The  water  of  wells,  springs  and  rivers  always  con- 
tains foreign  matter  in  solution,  derived  partly  from  the  air, 
partly  from  the  rocks  and  soil  and  partly  from  animal  or  vege- 
table sources.  These  substances  are  usually  present  in  a 
solution  of  such  h  gh  dilution  that  for  their  detection  the 
ordinary  methods  ol  analysis  must  be  somewhat  modified.  In 
considering  these  sp  .'cial  methods,  no  account  will  be  taken  of 
mineral  waters,  the  consideration  of  which  does  not  lie  within 
the  scope  of  this  vork,  but  only  those  constituents  will  be 
regarded  which  are  likely  to  be  met  with  in  the  natural  waters 
used  for  culinary  p  arposes. 

We  have  to  con  dder :  first,  the  normal  constituents ;  second, 
the  constituents  w  lich  are  due  to  contamination  of  some  sort. 

362.  The  ni  rmal  constituents  of  potable  water  which  are 
most  commonly  .net  with  are  the  following: 

a.  The  car'jonates,  chlorides,  and  sulphates  of  calcium, 
magnesium  a  id,  in  smaller  amounts,  of  sodium  and,  more 
rarely,  potas;*ium. 

b.  Ferrjus  and  ferric  salts  of  the  acids  named  are  often 
present  i^  small  quantities,  and  also  traces  of  aluminium  com- 
pound? and  of  silicic  acid.^ 


>  V/ater  containing  alumina  and  silicic  acid  is  usually  turbid,  from  clay  in 
'jspension.  Water  containing  iron  salts  becomes  turbid  upon  standing  and 
deposits  a  reddish  or  yellowish  sediment. 


Utef  eHMUmi^' 


-■mum 


Miiiwii»iwiiiWiyiini 


i 


«  * 


r. 


IVATBR. 

d  rivers  always  con- 
partly  from  the  air, 
from  animal  or  vege- 
usually  present  in  a 
their  detection   the 
mewhat  modified.     In 
count  will  be  taken  of 
ch  does  not  lie  within 
le  constituents  will  be 
\i  in  the  natural  waters 

1  constituents;  second, 

nination  of  some  sort. 

>table  water  which  are 

ing: 

sulphates  of  calcium, 

of    sodium  and,  more 

icids  named  are  often 
es  of  aluminium  com- 


jBually  turbid,  from  clay  in 
!S  turbid  upon  standing  and 


|J631 


ANALrSlS  OF  POTABLE    WATHR. 


93 


c.     Minute  traces  of  organic  matter    .     t    .    .   frequent. 
*'  **  ammonium  salt*       .     .     .     occasional, 

«  "  nitrates •• 

«•  «'  nitrites       •• 

Any  substances,  other  than  those  named,  which  may  be 
found  in  spring  or  river  water  can  be  regarded  as  abnormal 
and  as  constituting  a  contamination.  The  bodies  enumerated 
under  c  are  often  due  to  contamination,  and  always  so  when 
found  in  comptiratively  large  quantities.  (Compare  §378). 
The  commonest  abnormal  constituents  are  the  following: 

il.  Lead,  cop,  r  and  other  metals,  derived  from  pipeSi 
parups  or  similar  sources. 

e.  Tarry  or  oily,  or  other  odoriferous  matters  from  factory 
refuse,  etc. 

y.  Large  quantities  of  chlorides  are  often  but  not  always 
derived  from  sewage.  Anything  more  than  minute  traces  of 
the  substances  mentioned  under  "c"  are  probably  due  to  con- 
tamination with  animal  refuse.  If  much  organic  matter  is 
present,  without,  nitrogen  compounds,  it  is  usually  due  to 
decaying  vegetable  remains,  such  as  leaves,  sawdust,  peat, 
etc.,  etc. 

^.     Phosphates,  derived  from  sewage. 

363.  The  hardness  of  water,  that  is,  its  power  of  curd- 
ling soap  solution,  is  due  to  the  calcium  and  magnesium  salts 
which  it  contains.  The  carbonates  of  calcium  and  magnesium 
which  are  found  in  solution  are  not  the  normal  carbonates 
CaCOs  and  MgCOs,  but  are  the  unstable,  acid  carbonates, 
often  called  bicarbonates,  Ca(HC08)a  and  Mg(HCOg)3. 
The  latter  compounds  are  decomposed  when  the  solution 
containing  them  i^.  boiled,  the  normal  carbonules  of  calcium 
and  magnesium  being  precipitated. 

Ca(HC08),  =  CaCOg  +  HjO  +  CO, 
MgJHCOg),  ^  MgCOj  +  HjO  -f-  CO, 

We  find,  accordingly,  that  water  containing  the  carbonates 
and  bicarbonates  of  calcium  and  magnesium  becomes  softer 
when  boiled,  in  consequence  of  the  removal  of  these  salts 
from  solution. 


Conum* 
inatton. 


KardnesH 
of  water.  , 


I 


i, ,; 


m 


n 


..-S^^-^' 


&  I 


l;.  j 


1  I 


94 


SPECIAL   PART. 


f§365 


The  sulphates  and  chlorides  of  calcium  and  magnesium  are 

not  altered  by  boiling,  but  remain  in  solution.     We  therefore 

Permanent  distinguish  the  temporary  hardness  of  water,  which  is  due  to 

temporary  carbonates  and  which  is  removed  by  boiling,  from  the  ferma- 

hardness.    nciit  hardness,  which  is  due  to  the  sulphates*  of  calcium  and 

magnesium  and  is  not  affected  by  boiling. 

364*  Those  of  the  normal  constituents,  which  are  present 
in  larger  quantity,  may  be  detected  in  the  water  directly. 
Those  which  are  present  in  small  amount  are  to  be  tested  for 
after  the  water  is  concentrated  by  boiling. 

Always  note  carefully  in  observing  each  reaction  whether  it 
is  strongly  marked,  indicating  an  abundance  of  the  bod}'  tested 
for;   or  whether  it  is  barely  perceptible,  indicating  a  trace 

merely.                     '  .r  ■' ''.■''^■■■' ■'''■/■■"■■'■'-■■  ■""'""v' 

By  testing  both  before  and  after  concentration,  a  general 

idea  of  the  abundance  of  certain  constituents  may  often  be 
formed. 


■fU 


EXAMINATION   OF  THE   WATER    WITHOUT   PREVIOUS 
C0NCENT::AT10N.  ,        , 

365.     Take  for  each  test  50  c.c.  of  water. 

Chlorides,     a.     Acidify  with  nitric  acid  and  add  silver  nitrate;    a  curdy 
precipitate  indicates  chlorides. 

Sulphates.      b.     Acidify  with  acetic  acid  and  add  barium  chloride;  a 
white  precipitate  indicates  sulf  hates. 

Lime.  c.     Add  about  i  gram  of  ammonium  chloride,  then,  vvhen 

this  is  dissolved,  10  c.c.  ammonium  oxalate  solution;  a  white 
precipitate  indicates  calcium. 

If  a  precipitate  forms,  digest  in  a  warm  place  for  at  least 
five  hours  and  filter.  :,i^;r        "% 

Magnesia.      ^'    '^°  *^^  filtrate  add  sodium  phosphate,  then  20  c.c.  con- 
centrated ammonia ;  a  crystalline  precipitate,  forming  at  once 
or  afier  standing  several  hours,  indicates  magnesium. 
Iron.  e.     Acidify  with  hydrochloric  acid :  add  a  drop  of  potassium 

ferricyanide  solution.     A  blue  coloration  indicates  z.  ferrous 

'Or  chlorides. 


»>'*«!«WS*&<j»Si,' 


M^^ 


r«% 


ffl365 


land  magnesium  are 
lion.  We  therefore 
|er,  which  is  due  to 
ig,  from  the  -perma- 
|ites*  of  calcium  and 

»,  which  are  present 
the  water  directly, 
are  to  be  tested  for 

ya.  reaction  whether  it 
ice  of  the  bod}'  tested 
indicating  a  trace 

icentration,  a  general 
tituents  may  often  be 


THOUT   PREVIOUS 

water. 

ilver  nitrate;    a  curdy 

Id  barium  chloride;  a 

1  chloride,  then,  when 
ilate  solution;  a  white 

irm  place  for  at  least 

>hate,  then  20  c.c.  con- 
jitate,  forming  at  once 
i  tnagnesium. 
id  a  drop  of  potassium 
an  indicates  di  ferrous 


[§367 


ANALTS/S  OF  POTABLE   WATER. 


95 


salt;    '.  none  appears,  add  a  drop  of  potassium  ferrocyanide  Iron, 
solution,  when  the  mixture  will  turn  blue,  if  2i  ferric  salt  is 
present. 

f     Add  2  c.c.  of  Nessler's  reagent*  (§40);  a  yellowish  or  Ammonia, 
brownish  color  shows  the  presence  of  ammonia. 

^.     Acidify  with  hydrochloric  acid  and  add  a  drop  of  potas-  Nitrites. 
sium  iodide  solution  and  i  c.c.  of  starch  paste  (§§244,  245). 
A   blue   color  appearing   within   ten   minutes  indicates   the 
presence  of  «/Vr//«. 

This  test  is  useless  in  the  presence  of  ferric  salts,  which  give 
a  similar  indication. 

In  case  iron  has  been  found,  apply  Zambelli's  test  (§374)  to 
another  portion  of  the  water. 

//.     Organic  matter  may  sometimes  be  detected  by  the  odor 
which  is  evolved  when  a  sample  of  the  water  is  boiled,  either 
alone  or  mixed  with  pure  milk  of  lime  (/.  e.  calcium  hydrate         \ 
suspended  in  water). 

More  positive  tests  are  given  in  §§375-377. 

EXAMINATION   OF  THE    WATER    AFTER    CONCENTRATION. 

366.  Add  acetic  acid  in  slight  excess  to  one  litre  of  the 
water.     Evaporate  in  a  porcelain  dish  to  one-tenth  the  original  Fe,  Al,  • 
volume.     If  much  calcium  sulphate  was  present,  a  part  of  it  ""'^ 
may  crystallize  out  during  the  evaporation.     Filter,  if  neces-       "' 
sary.     Test  the  precipitate  fo/  iron  (§97),  aluminium  (§§64, 

335),  silica  (§§228,  232).  :• 

Divide  the  filtrate  into  several  parts.  These  parts  are  to  be 
used  for  any  of  the  tests,  «,  3,  c,  </,  e,  of  §365,  which  gave 
negative  results  with  .the  unconcentrated  water.  1  ;' 

>  Detection  of  Nitrates.  .  ' 

367.  Test  10  c.c.  of  the  filtrate  (preceding  paragraph) 

for  nitrates,  as  follows.     Mix  with  10  c.c.  of  concentrated  sul-  Indigo 
phuric  acid  and  add  to  the  mixture,  while  hot,  a  drop  of  indigo  *"*  *°'"    ► 
solution.'      If  this   turns  yellow   or  colorless,   nitrates    (or 

»See  List  of  Reagents,  Table  IV. 

'Enough  indigo  should  be  added  to  the  mixture  to  impart  a  very  pale,  but 
distinct,  blue  to  the  same  volume  of  distilled  water. 


^LtHg^f^-M 


.■■?'*^lw^.- 


w 


f..i  i 


r.'l 
'I'l 


■J ! 


Ml 


■!!1 


'1 1 


A  <  I 


96 


SPECIAL  PART. 


[§370 


Nitrates. 


nitrites)  are  present,  but  if  the  mixture  remains  blue,  nitrates 
are  not  present  in  notable  quantities. 

If  nitrites  are  present  (§365,;^),  they  must  be  removed  before 
testing  for  nitrates.  To  accomplish  this,  mix,  with  the  concen- 
trated sample  of  water,  one-half  gram  of  ammonium  chloride 
and  evaporate  to  dryness  on  a  water  bath.  This  decomposes 
the  nitrites,  but  not  the  nitrates. 

NaNO,  +  NH4CI  =  NaCl  =  2U2O  +  N, 

The  residue  is  to  be  tested  for  nitrates  as  described  above 
(or  below). 

368.  Mix  10  c.c.  of  the  filtrate  with  20  c.c.  of  concen- 
'  trated  sulphuric  acid.     After  cooling,  add  a  minute  fragment 

of  diphenylamine.  If  the  mixture  turns  blue,  nitrates  are 
present.  This  reaction  is  much  more  sensitive  than  the  pre- 
ceding. 

Detection  of  Lead  and  Copper. 

369.  If  lead  or  copper  are  suspected  they  may  be  tested 
Cu  and  Pb. '^°'"»  ^"  5**  ^'^'  °^  *^^  filtrate  (§366),  with  hydrogen  sulphide 

(§§130,  137).  If  a  black  precipitate  forms,  dissolve  it  in  a 
little  concentrated  nitric  acid,  drive  off  most  of  the  excess  of 
acid  by  the  application  of  heat  and  test  one  portion  of  the 
solution  for  lead  (§134),  another  for  copper  (§140). 

Detection  of  Phosphates. 

370.  To  another  portion  of  the  fiUrate  add  a  little  nitnc 
acid  and  evaporate  to  dryness.  Treat  the  residue  with  a 
small  quantity  of  water,  filter,  and  test  for  phosphoric  acid 
with  ammonium  molybdate  (§212). 

Instead  of  examining  a  concentrated  sample  of  the  water 
for  phosphates,  they  may  advantageously  be^detected  by  the 
following  process. 

To  one  litre  of  the  water  add  i  c.c.  of  ferric  chloride  and 
X  c.c.  of  sodium  acetate  solution.  Boil  for  five  minutes  and 
allow  the  precipitate  to  subside.  Decant  the  clear  portion  and 
filter  the  remainder.  Dissolve  the  precipitate  in  a  small  quan- 
tity of  dilute  nitric  acid  and  test  with  ammonium  molybdate 
for  phosphoric  acid  {/.  c). 


H.PO.. 


Precipi- 
tation of 
FePO«. 


II370 
*tnains  blue,  nitrates 

1st  be  removed  before 
pix,  with  the  concen- 
atnmonium  chloride 
.     This  decomposes 

|2HaO  +  Na 
as  described  above 

th  20  c.c.  of  concen- 
d  a  minute  fragment 
ns  blue,  nitrates  are 
ensitive  than  the  pre- 

JOPPER. 

ed  they  may  be  tested 
ith  hydrogen  sulphide 

forms,  dissolve  it  in  a 
most  of  the  excess  of 

test  one  portion  of  the 

)pper  (§140). 

ATES. 

L'rate  add  a  little  nitric 
lat  the  residue  with  a 
;st  for  phosphoric  acid 

d  sample  of  the  water 
isly  be^detected  by  the 

.  of  ferric  chloride  and 
(oil  for  five  minutes  and 
int  the  clear  portion  and 
:cipitate  in  a  small  quan- 
i  ammonium  molybdate 


§37^1 


ANALrSIS  OF  POTABLE   WATER. 
Detection  of  Sodium  and  Potassium. 


97 


371'  Concentrate  one  litre  of  water  in  a  porcelain  vessel 
to  about  one-tenth  its  volume.  Add  enough  barium  hydrate^ 
to  make  the  reaction  distinctly  alkaline  to  turmeric  paper. 
Boil,  filter  and  evaporate  the  filtrate  in  a  platinum  or  porcelain 
dish  to  the  volume  of  about  5  c.c.  and  filter.  To  the  filtrate 
add  I  c.c.  ammonium  oxalate  solution,  then  boil  and  filter. 
Evaporate  the  filtrate  to  dryness;  heat  the  residue  to  dull  k  and  Na. 
redness;  after  cooling,  dissolve  in  5  c.c.  hydrochloric  acid  and 
filter.  The  filtrate  may  be  tested  for  sodium  and  potassium 
by  the  flame  reaction  or  it  may  be  mixed  with  platinum  chlo- 
ride and  the  mixture  allowed  to  evaporate  on  a  watch  glass  in 
a  -place  free  from  ammonia  fumes.  If  sodium  and  potassium 
are  present,  their  chloroplatinates  will  appear  in  crystals  of 
characteristic  form  (§33).*  i^ 

Detection   of   Ammonium. 

Sy^*     Solutions  of  ammonium  salts  when   treated  with 
Nessler's  reagent'  (§40)  give  a  brownish  precipitate,  or,  if  the  Nessler's 
solution  is  very  dilute  and  free  from  salts  of  calcium  and  mag-  ^^    "^ 
nesium,  a  yellowish  or  brownish  coloration. 

This  test  may  be  applied  to  the  original  water  or,  when  the 
amount  of  ammonium  present  is  exceedingly  minute,  to  a. 
sample  in  which  the  ammonia  has  been  concentrated  by  distil- 
lation, as  follows: 

Introduce  half  a  litre  of  the  water  into  a  flask  attached  to  a  Testing 
condenser  and  render  it  strongly  alkaline  with  a  solution  of  the 
sodium  hydrate  which  has  been  boiled  to  free  it  from  ammo-  «''**'"»'«• 
nia.     Distill  the  mixture  until  50  c.c.  has  distilled  over.     To 

>Thi8  reagent  must  b«  free  from  the  alkalies.  After  trailing  with  an  excess 
of  ammonium  carbonate  and  subsequent  filtration,  the  filtrate  must  leavo  no 
residue  when  evaporated  to  dryness. 

*Not  infrequently,  the  amount  of  sodium  and  potassium  salts  present  may  be 
too  small  to  detect  in  one  litre  of  water.  In  such  cases  a  larger  amount,  such  as 
five  litres,  can  be  employed.  A  similar  remarli  applies  equally  to  the  detection 
of  phosphoric  acid.  Usually,  however,  it  is  not  worth  while  to  examine  larger 
amounts  than  one  litre  for  a  single  test,  except  in  connection  with  a  quantita- 
tive analysis.  ' 

•  Vide  Table  IV. 


il 


t'  i 

Vi'' 


l.-ii 
- 1'^  I 

Hi    ■ 

f:i! 


r  I 


"I    : 


l!  i 


'•!:! 


:n 


i 


.  •> 


m 


s» 


98 


SPECIAL  PART. 


[§37« 


the  distillate  add  2  c.c.  of  Nessler's  reagent,  when  the  presence 
;  of  ammonia  will  be  indicated  by  a  brownish  coloration.     An 

approximate  judgement  of  the  amount  of  ammonia  can  be 
formed  from  the  depth  of  the  color  produced. 

Detection  of  Nitrites. 

373.  If  no  nitrates  were  detected  before  concentration 
(§365,^^),  take  500  c.c.  of  the  water  and  add  enough  pure 
milk  of  lime  to  render  it  alkaline  to  turmeric  paper.  Boil  it 
down  rapidly  in  a  porcelain  dish  to  about  one-tenth  its  original 
volume  and  filter  it.  Test  the  filtrate  for  nitrites  according  to 
§365,  g',  or  the  following  section.  It  will  be  free  from  iron, 
unless  organic  matter  was  present. 

374.  The  most  delicate  reaction  for  nitrites  is  the  follow- 
ing, which  is  known  as  Zambelli's  test.  To  50  c.c.  of  the 
water  1  add  5  c.c.  of  a  saturaied  solution  of  sulphanilic  acid, 

t«rfor'"'C6H4NHaS08H,  and  5  c.c.  of  dilute  sulphuric  acid.  AUow 
nitrites,  the  mixture  to  stand  for  ten  minutes,  then  add  2  drops  of  a 
saturated  solution  of  phenol  ("carbolic  acid")  in  water.  Add 
ammonia  to  alkaline  reaction.  The  appearance  of  a  yellow 
color  indicates  a  nitrite.  This  test  will  show  the  presence  of 
1  part  of  nitrite  in  100,000,000  parts  of  water. 


Odor  of 
residue. 


Perman- 
ganate 
test. 


ORGANIC    MATTER. 

375,  Organic  matter  may  sometimes  be  detected  by  the 
odor  which  is  evolved,  when  the  residue  left  by  the  evapora- 
tion of  a  litre  of  water,  is  heated,  and  by  the  charring  of  this 
residue. 

376.  The  decolorizing  of  an  acidified  solution  of  potas- 
sium permanganate  by  organic  matter  mayjbe  used  as  a  test 
for  the  lattc. 

Add  25  c.c.  dilute  sulphuric  acid  to  200  c.c.  of  the  water 
and  then  add  enough  dilute  potassium  permanganate  solution 
to  color  the  whole  pale  violet.  From  i  to  5  drops  of  the  per- 
manganate will  usually  be  sufficient.     Heat  the  whole  to  boil- 


»The  original  water  may  be  used,  or  a  sample  which  has  been  boiled  down 
according  to  the  directions  of  §373. 


m 


^H. 


"      [§37« 

|t,  when  the  presence 
lish  coloration.    An 
[of  ammonia  can  be 
Lced. 


before  concentration 
Ind  add  enough  pure 
Imeric  paper.  Boil  it 
It  one-tenth  its  original 
ir  nitrites  according  to 
|rill  be  free  from  iron, 

nitrites  is  the  foUow- 

it.     To  50  c.c.  of  the 

!on  of  sulphanilic  acid, 

ulphuric  acid.     Allow 

then  add  2  drops  of  a 

acid")  in  water.     Add 

ppearance  of  a  yellow 

1  show  the  presence  of 

E  water. 

BR. 

nes  be  detected  by  the 

ue  left  by  the  evapora- 

by  the  charring  of  this 

lified  solution  of  potas- 
r  mayjje  used  as  a  test 

I  2cx>  c.c.  of  the  water 

permanganate  solution 

I  to  5  drops  of  the  per- 

Heat  the  whole  to  boil- 

which  has  been  boiled  down 


§378] 


INTERPRETATION  OF  WATER  ANALTSES. 


99 


ing.     If  it  retains  its  color,  organic  matter  is  absent,  but  pres- 
ent if  it  is  quickly  made  colorless. 

377.  Many  kinds   of  organic   matter,   especially  those  ^     ^, 
which  are  ^"«und  in  contamination  of  excrementitious  origin,  are  teat  for 
indicated  with  great  delicacy  by  Griess's  test.     To  50  c.c.  of  organic 
water    add    a    minute   quantity    of    benzolsulphodiazid,   and  *=°"^"'' 
make  the  solution  alkaline  with  ptire^    ammonia  or  sodium 
hydrate.     A  yellow  coloration  appears  if  organic  matter  of  the 

kind  referred  to  above  is  present. 

INTERPRETATION   OF  THE   RESULTS   OF  QUALITATIVE 
ANALYSIS  OF  WATER. 

378.  It  is  impossible,  in  many  cases,  to  conclude  defi- 
nitively from  the  results  of  a  qualitative  analysis  alone  whether 
a  given  sample  of  water  is  fit  for  drinking  purposes  or  not. 
Nevertheless,  valuable  indications  are  often  obtainec?..  Water 
which  contains  much  organic  matter  or  which  has  a  distinct 
odor  is  not  a  suitable  article  of  food,  and  should  always  be 
rejected  without  regard  to  further  results  of  analysis.  Such 
water  favours  the  reproduction  and  development  of  micro- 
organisms which  may  be  more  or  less  noxious.  Water  con- 
taminated with  organic  matter,  more  especially  if  this  be  of 
animal  origin,  when  kept,  undergoes  a  change,  through  the 

vital  processes  of  organisms  of  a  low  order,  by  which  the     ^?f,'" 
organic   substances   are,   in   part,   converted   into   ammonia,  of  the 
nitrites  or  nitrates.     If  therefore  more  than  slight  traces  of  the  organic 
last  named  compounds  are  found,  this  may  be  taken  as  an  '"*"^''- 
indication  that  the  water  had  at  a  former  period  been  contam- 
inated with  organic  liiatter.    Such  water  should  be  condemned, 
because  germs  of  the  micro-organisms  above  mentioned  may 
remain  after  the  decomposition  of  the  original  organic  matter. 
When  the  putrefactive  changes  are  continued  for  a  long 
time,  nitrates  only  may  be  found,  with  or  without  nitrites  or 
ammonia. 

>It  is  absoluteljr  necessary  to  test  the  purity  of  the  reagents  by  mixing  them 
with  50  c.c.  of  distilled  water.  The  mixture  will  remain  colorless  if  they  are 
free  from  organic  impurity. 


WWitjim 


immiimmmmmmmmmmmmmimm^M- 


^ 


I 
I 


■M 


lOO 


Rain- 
water. 


SPECIAL  PART. 


r§378 


Sewage. 


Boiler 
scale. 


Rain-water  collected  from  roofs  and  stored  in  cisterns  is 
often  rich  in  organic  matter  derived  from  dust,  leaves,  etc.,  on 
the  roof.  The  pollen  from  numerous  kinds  of  trees  is  a  pro- 
lific source  of  organic  contamination  of  the  cistern  water  in 
some  localities.  The  absence  of  anything  more  than  mere 
traces  of  chlorides  from  waters  such  as  this  distinguishes  them 
at  once  from  those  which  have  been  contaminated  by  sewage 
or  through  underground  leakage  from  cesspools,  although 
the  abundant  nitrogen  compounds  sometimes  found  in  the 
former  might  lead  to  the  presence  of  animal  refuse  being 
suspected. 

If  the  quantity  of  chlorides  is  considerable  and  if,  at  the  same 
time,  distinct  reactions  are  obtained  for  nitrites,  ammonia  or 
organic  matter,  the  water  is  to  be  unhesitatingly  condemned, 
on  the  ground  that  it  is  probably  contaminated  with  sewage  or 
animal  excreta  in  some  form,  since  the  latter  contain  sodium 
chloride  in  abundance  and  also  nitrogen  compounds.  In  cases 
of  suspected  sewage  contamination,  Griess'  test  (§377)  is  very 
valuable.  But  if  it  fails  to  give  any  positive  indication,  the 
water  is  not  therefore  necessarily  safe,  because,  as  already 
explained,  the  germs  of  disease  may  remain  after  the  original 
ot^anic  contamination  is  destroyed  by  decomposition  into 
ammonia,  etc. 

Water  containing  much  calcium  and  magnesium,  that  is, 
water  w!iich  is  very  hard,  is  not  necessarily  unwholesome,  but 
is  unsuitable  for  mechanical  purposes.  Such  water,  when 
used  to  supply  steam  boilers,  produces  an  incrustation  or  scale 
which  interferes  with  the  development  of  steam  and  greatly 
shortens  the  life  of  the  boiler. 

The  composition  of  the  scale  depends  upon  that  of  the 
water.  It  often  consists  of  calcium  and  magnesium  carbonates 
mixed  with  calcium  sulphate  and  magnesium  hydrate. 

"Water  containing  much  magnesium  sulphate  (or  chloride) 
frequently  corrodes  the  boiler  plates  quite  rapidly,  in  conse- 
quence of  the  formation  of  free  acid  and  basic  salts. 
MgCla  +  H2O  =  MgClOH  +  HCl 


i. 


»-* 


r§378 

■stored  in  cisterns  is 
dust,  leaves,  etc.,  on 

[nds  of  trees  is  a  pro- 

the  cistern  water  in 

ig  more  than  mere 

Lis  distinguishes  them 

pminated  by  sewage 
cesspools,   although 

letimes  found  in  the 
animal  refuse  being 

ble  and  if,  at  the  same 

nitrites,  ammonia  or 

sitatingly  condemned, 

inated  with  sewage  or 

latter  contain  sodium 

compounds.     In  cases 

jss'  test  (§377)  is  very 

positive  indication,  the 

because,  as  already 

main  after  the  original 

)y  decomposition  into 

d  magnesium,  that  is, 
arily  unwholesome,  but 
.  Such  water,  when 
an  incrustation  or  scale 
t  of  steam  and  greatly 

:nds  upon  that  of   the 
magnesium  carbonates 

esium  hydrate, 
sulphate  (or  chloride) 

quite  rapidly,  in  conse- 

d  basic  salts. 

H  +  HCl 


[§38a 


ANALYSIS  OF  ALLOYS. 

ANALYSIS  OF  ALLOYS. 
PRELIMINARY     EXAMINATION. 


379.  Heat  on  charcoal    before    the    blowpipe    (§13). 
Arsenic,  antimony,  zinc,  lead,  bismuth,  and  sometimes  tin  and  etcetgcg' 
silver  may  be  detected  by  their  reactions  as  described  in  the 
directions  given  under  the  headings  of  those  metals. 

380.  Heat  in  a  matrass  (§14).  Mercury  is  indicated  by 
a  gray  sublimate.  Cadmium  and  'arsenic  may  also  form 
sublimates  which  can  be  easily  distinguished  from  that  of 
mercury.     (§§127.  166). 

A  fuller  outline  scheme  for  the  blowpipe  examination  of 
alloys  is  given  in  Table  I  (p.  104). 

SOLUTION. 

381.  Gold  and  platinum  are  not  attacked  by  nitric  acid. 
Antimony  and  tin  are  oxidized  by  nitric  acid,  but  the  resulting  hno.  on 
oxide  of  the  former  is  nearly  and  that  of  the  latter  quite  alloys, 
insoluble  in  both  water  and  nitric  acid. 

Aluminium  and  some  of  its  alloys,  distinguishable  by  a  low 
specific  gravity,  are  scarcely  attacked  by  nitric  acid.  Hydro- 
chloric acrd  is  the  best  solvent  for  aluminium  and  the  alloys 
referred  to. 

All  other  metals  are  oxidized  by  nitric  acid,  the  resulting 
oxides  being  converted  into  nitrates  which  dissolve. 

382.  Warm  the  substance  with  a  mixture  of  nitric  acid 

and  water  in  equal  parts.  If  the  alloy  completely  dissolves,  solution 
either  at  once  or  after  the  addition  of  more  water,  gold,  plati-  *"  HNO,. 
num  and  tin  are  absent,  and  only  traces  of  antimony  can  be 
present.  Proceed  with  the  solution  according  to  the  general 
scheme  (§324,  et  seq.)^  first  removing  most  of  the  nitric  acid,  if 
it  is  present  in  great  excess,  by  evaporation  nearly  to  dryness 
and  subsequent  dilution.  If  a  precipitate  is  thrown  down 
when  the  solution  is  diluted,  bismuth  is  probably  present 
(§147).  In  this  case,  filter,  wash  the  precipitate  and  then  boil 
it  with  sodium  hydrate  and  stannous  chloride.  If  it  turns 
black  {v.  §152)  the  presence  of  bismuth  is  confirmed. 

For  the  detection  of  the  metals  in  the  solution,  pass  to  §324. 


\1^ 


^■-V■ 

:| 

t 


fe5li^^->!4i3gS(Sa*«fe*>'*^'^^^^^  -  ■'^"**    ¥fv»^ij4sii>fc*<si*^w^<ii.- 


I03 


SPECIAL  PART. 


[§38S 


cf! 


Sb,  Sn 

and  As. 


383.  If  a  residue  is  left,  insoluble  in  nitric  acid  and  water, 
it  may  consist  of  gold,  platinum,  metastannic  acid  or  metanti- 
monic  acid. 

Au  and  Pt.  If  it  is  metallic,  dissolve  it  in  aqua  regia  (four  parts  of  con- 
centrated hydrochloric  to  one  of  nitric  acid)  and  test  the 
solution  for  gold  and  platinum  (§§183,  186). 

If  the  residue  is  a  white  powder,  tin  or  antimony  is  indicated, 
and  the  precipitate  may  also  contain  arsenic  acid.  Test  the 
residue  for  antimony,  tin  and  arsenic  according  to  §§164, 170, 
179,  180,  and  for  bismuth  (§152)- 

384.  The  insoluble  residue  may  with  advantage  be  ex- 
Blowplpe  amined  in  the  following  way  after  washing  and  drying, 
examina-       jjeat  One  portion  in  a  matrass  (§14)  with  a  little  dry  potas- 
'rwlduV''*'  *'"™  cyanide.     An  arsenical  mirror  will  appear  if  this  metal  is 

present.  If  it  does  so,  cut  off  the  lower  end  of  the  tube  and 
cautiously  heat  the  mirror  so  as  to  oxidize  it.  If  it  be  arsenic, 
it  will  form  the  characteristic  crystalline  film  of  colorless  octa- 
hedrons, distinctly  visible  imder  the  microscope. 

Heat  another  portion  on  charcoal  in  the  oxid'zing  flame. 
Arsenic  will  be  driven  off  and  antimony  will  form  a  film 
which  will  turn  greenish  when  heated  with  cobalt  solution. 
*  If  antimony  is  absent,  the  non-volatile  residue  consists  of 
SnOj,  which  m^  be  reduced  to  tin  with  the  cyanide  flux,  §165. 
385.  If  the  alloy  partially  dissolves  in  the  nitric  acid  but 
also  leaves  an  insoluble  residue,  examine  the  latter  according 
to  the  preceding  paragraph  and  analyze  the  solution  according 
to  the  general  scheme  (§324). 


Partial 
solution. 


.. .  11 


(I3t8 

|itric  acid  and  water, 
lie  acid  or  metanti- 

(four  parts  of  con- 
acid)   and  test  the 

mtimony  is  indicated, 
benic  acid.  Test  the 
)rding  to  §§164, 170, 

th  advantage  be  ex- 
ig  and  drying, 
vith  a  little  liry  potas- 
appear  if  this  metal  is 
r  end  of  the  tube  and 
ze  it.  If  it  be  arsenic, 
film  of  colorless  octa- 
•oscope. 

n  the  oxid'ting  flame, 
nony  will  form  a  film 
d  with  cobalt  solution, 
ile  residue  consists  of 
1  the  cyanide  flux,  §165. 
:s  in  the  nitric  acid  but 
ne  the  latter  according 
e  the  solution  according 


103 
ATOMIC  WEIGHTS  AND  QUANTIVALENCB  OP  THE  ELEMENTS. 

The  atomic  wrights  are  given  in  accordance  wittt  Me^cr  and  Seubert't  calculation*, 
excepting  in  case*  where  more  recent  determination*  have  made  change*  nece*«arj.  There 
i*  *o  much  that  i*  hvpotlietical  and  arbitrary  In  the  conception  of  quantivalence,  that  the 
number*  repre*enting  thi*  atomic  attribute  are,  unlike  tho*e  expre**lng  atomic  weight*,  to 
be  talien  w  ch  rc*erve  a*  presenting  theory,  In  many  case*  at  lea«t,  ratlier  than  a*  final  atate- 
ment*  o(  fact. 


Nam*. 

Sym- 
Sol. 

^uaiiti- 
valeHct. 

Atomic 
Weigkl. 

Name. 

'a: 

J^uanti- 
tHilence. 

Atomic 
Weight. 

Hydrogeii 

H 

I 

X 

Molybdenum 

Mo 

IV,  VI 

95-9 

Aluminium 

Al 

III 

37.04 

Nickel 

Ni 

II,  III 

58-56 

Antimony 

Sb 

III,  V 

1 19.6 

Niobium* 

Nb 

III,  V 

93-7 

Arsenic 

As 

III,  V 

74-9 

Nitrogen 

N 

III,  V 

14.01 

Barium 

Ba 

II 

136.86 

Osmium 

Os 

11,  IV,  VI,  VIII 

191. :3 

Beryllium 

Be 

III 

903 

Oxygen 

0 

II 

15.96 

Bi*muth 

Bi 

III,  V 

207.5 

Palladium 

Pd 

III,  IV,  VI 

io6.a 

Boron 

B 

III,  V(?) 

10.9 

Phosphorus 

P 

III,  V 

30.96 

Bromine 

Br 

I,  VII      « 

79.76 

Platinum 

Pt 

11,  tV,  VI,  VIII 

>94  34 

Cadmium 

Cd 

11 

111.7 

Potassium 

K 

I 

39-03 

Ciesium 

Cs 

I 

132.7 

Rhodium 

Rh 

II,  IV,  VI 

104.1 

Calcium 

Ca 

II 

399« 

Rubidium 

Rb 

I 

85-2 

Carbon 

C 

II,  IV 

U.97 

Ruthenium 

Ru 

III— VII 

103.5 

Cerium 

Ce 

III,  IV 

13987 

Samarium 

Sm 

(?) 

iSo(?) 

Chlorine 

CI 

I,  VII      > 

35-37 

Scandium 

Sc 

Ill 

43.97 

Chromium 

Cr 

III,  VI 

5245 

Selenium 

Se 

II,  IV,  VI 

78.97 

Cobalt 

Co 

II,  III 

58.74 

Silicon 

81 

IV 

38.33 

Copper 

Cu 

II,  I 

6333 

Sliver 

Ag 

t 

107.66 

Didymium 

Di 

IV 

'45- 

Sodium 

Na 

I 

33«) 

Brbium 

E 

II 

166. 

Strontium 

Sr 

II 

87-3 

Fluorine 

F 

I,  VII 

19.06 

Sulphur 

S 

II,  IV,  VI 

31-98 

Gallium 

Ga 

IV 

69.9 

TanUlum 

Ta 

V 

183. 

Germanium 

Ge 

IV 

72-31 

Tellurium* 

Te 

11,  IV,  VI 

136.7 

Gold 

Au 

I,  III 

196.85 

Thallium 

Tl 

1,  III 

203.7 

Indium 

In 

III 

1 13-4 

Thorium 

Th 

IV 

232- 

Iodine 

I 

r,  VII    > 

126.54 

Tin 

Sn 

II,  IV 

II8.8 

Iridium 

If 

11,  IV,  VI 

192-5 

Titanium 

Tl 

11,1V 

48.01 

Iron 

Fe 

II,  III 

55-88 

Tungsten 

T 

III,  IV,  VI 

193.6 

Lanthanum 

La 

IV 

138.S 

Uranium 

U 

VI,  IV 

238-9 

Lead 

Pb 

II,  IV 

206.39 

Vanadium 

V 

III,  V 

5i-« 

Lithium 

LI 

I 

7.01 

Ytterbium 

Yt 

173.6 

Magnesium 

Mg 

II 

33.94 

Yttrium 

Y 

IV 

89.6 

Manganese 

Mn 

ii,iv,vi,vni 

54-8 

Zinc 

Zn 

II 

65.3 

Mercury 

Hg 

II.  I 

199.8 

Zirconium 

Zr 

IV 

90.4 

1  Probably  also  iii  and  v. 

■Also  called  Columbium,  Cb. 

■According  to  the  latest  researches,  the  atomic  weight  of  tellurium  Is  in  doubt. 


If 


I 


•- 1 


V-.  winiiiiwiiwwiiiiiiywiMiiiir- 


I'  / 


TABLE    I. 
BLOWPIPE  REACTIONS  OF  SINGLE  METALS  AND  ALLOYS. 


-Ilial  on  Ckarcoiil  in  tkt  0»it*'%ing  Flame:- 


A  whit*  incrHMlntion  is/armed. 


Aluminium:  Wliite  cortlng  on  and  near  aMav, 
Al  not  volatile  In  O.F.  or  R.F..  Infualble. 


Tin: 
Sn 


Couting  on  and  near  the  atmy  pole 
yellow  when  hot,  white  when  cold. 
Not  volatile  In  O.  F.  or  R.  F. 


Zinc. 
Zn 


Coating    III    the   charcoal    yellow 
when  hot,  whItUh  when  cold. 
Volatile  in  R.  F. 


Maonehium:  White  coating,  hot  and  cold. 
Mg  Not  volatile. 


Antimony: 
Sb 


White  coating  on  charcoal.    Vola- 
tile In  R.F.,  lei*  to  in  O.F.    No  odor, 


Arsenic:         White  coating  far  from  the  atiay, 
Ad  HlKhly  volatile  in  U.  F. 

Ailiaceou*  odor. 


Mercury: 
Hg 


Volatile  without  coating  or  odor. 


Flame 
coioration. 


Tit  coaling  motttentd  wilk  Co, 
Hoi. and  ignittd  in  O.  F.  btcomes 


White. 


None. 


Greenish 
white. 


White. 


Pale  grei  .1. 


Pale  blue. 


None, 


Sliy-bluc, 


Tea-green, 


YellowUh  green. 


Fleah-colored, 


Dull  darli  green. 


Heated  In  open  tube  gives 
white  gllitening  lublimate 
anedrai  crvtt 


of  octar 


crvttaU. 


Hected  In  a  matraas  gives  a 
mouse-gray  flim.    (§1^7.) 


2.      A  colored  incruitation  is  formed  on  the  Ck. 


Lead:  Coating  is  dark  yellow  when  hot, 

Pb  sulphur  yellow  cold.  Fusible.  Coat- 

ing gives  atnre  blue  to  R.  V, 


Bismuth  :        Coating  is  deep  orange  when  hot, 
Bl  lemon  yellow  cold.  Volatile.    Coat- 

ing imparts  no  color  to  R.  F. 


Silver: 
Ag 


Dark   red   coating    slowly    forms 
near  assay,  which  remains  bright. 


3t     Assay  oxidises  without  incrusting  charcoal. 


Copper : 
Cu 


Assay  fuses  and  turns  black  in 
O.  F.,  then  In  R.  F.  becomes  red 
Colors  the  flame  green,  moisten' 
ed  with  HCl  colors  flame  sky-blue 


Nickel  :  Assay  does  not  fuse,  turns  blue- 

Ni  black  In  O.  F.,  gray  in  R.   F 

Magnetic. 


Cobalt  : 
Co 


Like  nickel. 


Ikon:  Assay   turns  black   in  O.  F., 

Fe  same  in  R.  F.      The  oxide  is 

magnetic. 


Manganese:  Assay  turns  reddish  brown  in 

Mn  O.  F.  and  then  does  not  change 

in  R.  F.    Infusible 


Chromium  :     Assay  turns  dark  green  In  O.  F 
Cr  and   then  Joes  not  change  In 

R.  F.     Infusible. 


Azure  blue. 


None 


Pale  violet. 


Healed  on  Ch.  witk  sulfkur  >t 
Kl  a  coating  is  formed  which  is 

Bright  yellow. 


Red, 


orange,  and 


yellow. 


or  ax  Bead  in 
O.  F. 


Hut,  green. 
Cold,  blue. 


Hot,  violet. 
Cold,  brown. 


Blue. 


Hot.vlolet  to  black 

Cold,  violet  to 

amethvst. 


Hot,  yellow  to  red 

Cold,  yellowish 

green. 


Hot,  yellow  to  red 

Cold,  colorless  to 

yellow. 


Borax  Bead 
in  R.  F. 


Red  and 
opaque. 


Groy  to 
colorless. 


Blue. 


Bottle-green 


Colorless. 


Hot,  green. 
Cold,  green. 


Soda  Bead  in 
O.  F. 


Hot,  green. 
Cold,  white 
and  opaque. 


Insoluble. 


Hot,  pale  red. 
Cold,  gray. 


Insoluble. 


Deep 
grass-green. 


Hot,  brownish 
yellow.  Cold, 
lemon  -  yellow. 


Assay  does  not  oxidne  nor  form  coating. 


Gold: 

Au 

Platinum: 

Pt 

Mercury: 

Hg 

Assay  fuses,  otherwise  no  change. 
Infusible,  no  change. 
Vola.iiizes.    (See  above.) 


Abbreviations  : 

Ch.,  Charcoal. 

O.  F.,       Oxidizing  flame. 

R.  F.,       Reducing  flame. 

Co.  Sol.,  Cobalt  nitrate  solution. 


♦.«► 


LND  ALLOYS. 


J  coaling  moi»teMii  with  Co. 
|<»i</  igHJItdin  O.F.  btcomti 


Skyblu*. 


Tea-gr'ien. 


Yellowish  green. 


Flesh-colored. 


Dull  darl(  green. 

rieated  in  open  tube  gives 
irhite  glUtening  sublimate 
f  octahedral  crystals. 

lected  In  a  matrass  gives  a 
nouse-gra)*  film.    ({(iJ?.) 

(eated  on  Ck.  wi'/A  smlfhur  it 
'I  a  coating  is  formed  which  is 

Bright  yellow. 


Red, 


orange,  and 


yellow. 


Bora*  Bead 
in  R.  F. 

Soda  Bead  in 
O.  F. 

Red  and 
opaque. 

Hot,  green. 
Cold,  white 
and  opaque. 

Gray  to 
colorless. 

Insoluble. 

Blue. 

Hot,  pale  red. 
Cold,  gray. 

Bottle-green. 

Insoluble. 

Colorless. 

Deep 
grass-green. 

Hot,  green. 
Cold,  green. 

Hot,  brownish 
vellow.     Cold, 
lemon  -  yellow. 

nations: 

Charcoal. 
'.,       Oxidizing  flame. 
'.,       Reducing  flame. 
So\.,  Cobalt  nitrate  solution. 


'$ 


u. 


III 


oa 


i-^ 

0.  c 

1 

CO 
CL. 

y 

A. 

CO 

75  8 

2^S 

u 

75 

<  1 

flu  75 

(0 

■ 

N 

-<    1 

0.7) 

U  tj 

u 

Cfl 

-1 

•< 

1 

(O 

o. 

11 

7) 

75  8 

1 

73 

<    1 
0U75 

-<    1 
BU73 

<   1 
04  7} 

a 

0. 

tn 

75 

1 
75 
(U 

73 

75 

K 

2 

^1 
CO  o. 

1 

V) 

& 

y 

0. 

75 

<    1 
0U73 

1 
73 

flu 

73 

<    1 

0.75 

<    1 
0,75 

1^ 

•<  1 

euco 

CO 

1 

7) 

«l 

<    1 
flu  75 

1 
75 

a 

1 
73 

eu 

^1 

Oh  75 

<    1 

euTi 

<  1 

4-^ 

a. 

O. 

Suco't 

CO 

1 
75 
Ou 

0. 

73 

<    1 
Ou75 

-<  1 

0.73 

0. 
3 
0 

cc 
0 

6  % 
U  1 

<  1 

ft.W 

0 

i 

a. 

•l 
CO 

"1 

75 

1 
75 

eu 

I 

75 
0. 

+ 
(^    1 
75 

flu  75 

<    1 
CUT] 

o 

B 
Z 

CO 

eu 

CO 

CO 

<  1 

(Li75 

<    1 

eu(0 

+ 
73 

^1 

Ql<75 

•< 

0. 

'it 

qI 

1 

y  1 

^  1 

1 

1." 

-,| 

<    1 

^ 

3 
0 

C 

<s 

Q 

1 

li     ■ 

>j  ai  « 

Cfl 

^4- 

CO 

Oh 

Ceo 

a75 

75 

eu 

75*  c 

73 

CU75 

1 

t/i 

__ou   _ 

y 

1 
W 

a. 

o 

CO 

7)  U 

eu  i 

b. 

y 

75 

1 

CO 
0. 

1 

75 

A. 

•^ly 

<    1 
0U75 

iJ 

1 

CO 

eu 

y  1 

aco 

y  1 

euT) 

75 

a 

1 
75 

CL. 

^1 

73 

0U 

<    1 
(Li  75 

sJ 

a 

1 

CO 

cu 

Ph 

"  1 

eu'A 

CO 

1 
75 

eu 

75  *  g 

75 

<!  1 
a<75 

:J 

a 

A  ?i  « 

C/} 

y 

y 

y 

y 

y 

y 

75 

y 

y 

A 

3 
0 

c 

(9 

0 

CO 

CO 

CO 

Vi 

73 

75 

75 

75 

1 

<>i^ 
^2*^ 

CO 

u 

y 

y 

y 

y 

75 

73 

y 

y 

7>| 

c 

2i5 

CO 

CO 

CO 

CO 

75 

■• 

75 

75 

1 

y 

y 

y 

y 

y 

y 

75 

y 

y 

1 

j<J?." 

CO 

CO 

CO 

7} 

75 

a 

75 

75 

1 

0 

•* 

-f 

1 

NAME   A 

SYMBO 

to 

H    - 

<o 

So? 
« 

•< 

u 
gc«! 

si 

<    •• 

i%6 

HOfieii 

ai 

So 

16 

X 

go, 

%0iiOS 

in^H 

1 

X 

CO 

y 

Cb 

O 

73 

<3 

y 

Oh 

°^H 

• 

rfnoue 

aiov 

•-* 

tsa 

fH 

mSa 

1 

1 


ft.    S 


Vi 


U     I  < 


75 


I 

:  I 


CO 


CA 
Vi 

a. 


V) 


V) 
0. 


I 


^ 


Cfl 


0. 


I 

OmCA 

<  I 


T 


<  I 

&.cn 


CO 


CO 

a. 


<  \   \  < 


bCO 


CO 

flu 


CO 

a 


coo 


CO* 


CO 

a. 


+ 


CO 


4- 


co 


<  I 

&ICO 


<  I 

Otco 

<  I 

Ok  CO 


<  I 

0.(0 

<  I 

OiCO 


•«!  1 


<  I 


<  I 

OiCA 


CO 

a 


CO 

EL. 


CO 

a 


CO 

0. 


U 

CO 


u 

B 


CO*"  E 


CO 


»} 


CO 

0* 


<  I 

Ok  CO 


a<co 


<  I 

OtCO 


0. 

-^  I 

0<C/i 


(UCO 


CO 


CO 


CO 


CO 


HOtfOt! 


CO 


o 

CO 


u 

CO 


On  CO 


CUM 


OhCA 


< 

cue/; 


CO 


73 


U 

CO 


o 

uO 
(-1  M 
<0i 

& 


s  r 
oai 

S 

U 


u 

CO 


CO 


CO 


So*, 

HCUO 

=  3=3- 

%oios 

s 


CO 


S  CQ 


L^Kui 


I 

0. 


04 


I 

a 
"I 


cuZ 


CO 


I 

CO 

a 

CO 


(0 


CO 


>■ 


4> 


I 

0. 


I 
CO 

a. 

IS 
0.2 


CO 


CO 


U 

CO 


I 

CO 


I 

CO 
CO 


co-s 


"I 


M 

0 

u 


CO 


CO. 


CO 


(0 


to 


CO 


u 

73 


u 

CO 


CO 


o 

CO 


CO 


CO 


u 

CO 

O 

CO 


H 

•< 

gco 

D 
CO 


CO 


CO 


CO 


CO 


2^ 
qoS 

S 

U 


CO 


CO 


(0 


CO 


CO 


CO 


Id 
H 

S 

So 

gu 


to 


CO 


CO 


CO 


w 


CO 


CO 


so 

So£ 


^1 


-■IS 

C3£ 


co.S 


o.-« 


ho«s 
a     m 


CO 


CO 


CO 


CO 


CO 


to 


CO 


X 


CO 


CO 


CO 


CO 


CO 


CO 


CO 


73 


CO 


i  CO 


to  f^ 


o 

to 


to'S. 


"I 

CO  >- 


to  ^ 


73 


u 


CO 


u 

CO 

o 

CO 


CO 


u 

73 


u 

73 


o 
n 


7)  C 


73 


73 


i 


to 


o 

CO 

o 

73 

u 

73 

u 

73 


o 

73 


CO 


o 

73 


H 

COS 

s 
o 


CO 


< 


73 

0.7}  ii 


^73 
0.* 


O 

75 

73  E. 

730 1 


<; 


<  I 

Cl73 


73 


I 
73 

C 


73 


73 


73 


73 


IS  04 

u 


73  C 


73 


73 


73 

o 

73 


73 


u 

73 


u 

73 


73 


73 


ooi 

Q 

O 


S^ 


73 -h 
0.    I 


■f- 
7i 

0. 


< 

73 


73 


4  U 

a.     tt 


I    -i 

o.      S 


u 

73 


73 


7) 


73 


73 


73 


73 


73 


73 


73 


73 


73 


73 


73 


73 


73 


-IS 

<  s 

H 
O 
< 


Mt. 


II 


H 


fi* 


,~t<;!W* 


M 


i 

'J  I 


n 


io8 


(A 

<< 

Q 

<! 

(0 
H 

(0 

(X. 

O 

(A 

U 


09 

D 
>J 
O 
(A 


a 


•J 
S 


■     \^-       ■'fi" 

' .- . 

The  solubilities 
of  many  of  the 
sacs  enumerated 
in  this  Table  are 
materially  modi- 
fied by  the  pres- 
ence of   other 
salts  in  the  solu- 

tion ;    the    thio- 
sulphatesof  cop- 

per  or  lead  being, 
for  example. 

^    "o     -S     -^      I        £ 

1    8  1  S       i 
^    g  5   »       i 

>.  s:  E  "      ' 

is  °"  3  t;     « 

8  .S  1  -S.       1 

a. 

c 

CO 

i 

•9 

1 
75 

1 
73 

C/3       "■' 

0. 

1 

ft. 

5  2  = 

2  o  t^ 

w  1 

+ 

1 

1 

1 

3 
0 

c 

(9 

Z 

«■+ 

CO 

CO 

a. 

CO 

Ol 

CO 

75 
ft. 

73 

73 

ft. 

i 

a. 

3  = 

(1.  1  § 

8 

(J 

(i 

u 

l- 
>< 

0^ 

•a 

"a 

(0 

U     * 
(/)  O  00 

1 

■ 

^Z< 

CO 

CO 

CO 

a. 

tix. 

1,7: 

1 

^ 

1 

1 

1 

1 

"i+i 

CO 

a. 

CO 

CO 

Ol 

75 

73 

a. 

a 

P  s 

am.  dec 
brown 

^11 

75 

1 

1   , 

i,i 

1 
73 

ill 

« 

CO 

Ol 

St, 

a, 

O. 

ft. 

&.•«>. 

-   Mer- 
curic. 

CO   M 

^0 

I.I 

1 
CO 

a 

1 

CO 

a. 

1 
75 

Oh 

ft.  W) 

1 
75 

04 

"3     . 

Ol 

Id  OS 

1   o-g 

1 

CO 

CU 

1 

CO 

0. 

1 
73 

i^l 

1 

75 

3 
0 
C 
(9 

S"* 

0.^-° 

c 

CU 

ft. 

c-e 

ft. 

Q     , 

Cfi  + 

-t- 

!« 

1 

1 

1 

1 

1 

II 
0.S, 

1 

X 

H  Bu 

al 

7J 

CO  u 

CO 

CO 

CO 

0. 

75 

ft4 

75 

ft. 

73 

ft. 

ft. 

0  Mm 

co3 

1     u    = 

i,      bo 

1. 

C03 

1    01   u 

l-s" 

C0S..2 

1      ■= 

75  u 

ft.  M 

Ig 

CO  <u 

ft.  !ai 

"1 

43 

!g 

73  u 

ft.  & 

^  ^ 

U 

73 

1 
CO 

1 

CO 

1 

CO 

1 

CO 

1 
73 

1 

73 

^1 

1 

73 

ft. 

O-iJi  a 

0* 

a. 

Ol, 

a 

ft. 

•h. 

ft.^ 

ftn 

II 

— u 
oa  g 

^n 

■a 

CO 

1 
CO 

1 

CO 

1 
75 

1 
73 

75  0 

1 
75 

H 

1 

CO  t) 

CO 

1-^ 

Oh 

Sh 

ft. 

ft. 

cui 

ft. 

H 

Q 

1 

Z    J 

S 

AME    A 
SYMBO 

in 

So 

a; 

Id 

5d 

a 

a^I 

i%6 

% 

1?: 

SO  , 
Hft,o 

<o 

5^ 

•/:'J 

HU 

bao 

<s< 

wO 

iSu 

§^ 

Eoi 

SoT 

^Qi 

lies 

■r    °« 

55    c»  CO 

<fti 

oos 

7*      w    « 

z, 

>• 

h1 

ot 

a 

•« 

s 

■ji 

Oi 

Di 

0 

H      iH 

►iN 

s 

< 

h! 

:>< 

S 

K 

0 

s 

s 

to 

U 

b 

0 

75 

<1 

03 

0 

ft. 

(0      B 

^ 

' 

^H 

dnouo 

aiov 

^ 

Sc<] 

H 

'"^mm^t^mk 


'■V^TLSin>'!d;l 


mmmmm 


1 

tion ;    the    thio- 
sulphates  of  cop- 

per  or  lead  being, 
for  example. 

readily     soluble, 
in     presence    of 
sodium    thiosul- 
phate,  which 

unites  with  them 
to  form  double 

salts.      In  view 
of   this  circum - 

stance,  the  state- 
ments of  the  ta- 

ble  are  to  be  re- 
garded  as  fully 
valid  only  when 
the  solution  con- 
tains nothing  ex- 
cept  water  "^nd 
the  specified 

acids  or  alkaline 
hydrates. 

H 

1 

o<  % 

1 

CO 

1  = 

CO  i5 

CO  il 

1- 

04 

ft-    !-> 

1 

1 

1 

2<  P 

■ 

« 

1 

CO 

73 

1 

flu 

co 

1  8 

CO 

CO 

CO 

73 

'0. 

CO 

1 

(U 

cu 

CU 

ft, -a 

I '' 

o. 

1 

CO 

cu 

ftl  J3 

»l 

0 

1 

ft. 

-1 

43 

« 

1 

eu 

:><  a 

11 

cng 

co:2 

u 

CO 

^1 

CO 

1 

<^ 

1  F 

M 

CO 

CO 

73 

ft.  -  ■ 

1 

1 

Z<  i> 

1 

1 

0 

CO 

1 

1^ 
1  n 

»l 

0. 

73 

CO 

^ 

a 

ft.S 

1 
CO 

1. 

CO  JJ 

Hi 

!eI 
a, -a  51. 

1 

1 

CU 

1 

cu 

1 
cu 

a 

ft.^ 

cog 

ft. -a 

1  » 

flu  "3 

1 

Cu 

jjIcOrt 

73 
ft. 

ll 
Ouu 

ft.  «« 

73 

1 

1 

CO 

&4 

1 

CO 

b 

ft.^ 

US 

U 

CO 

CO 

CO  "2 

ft. 

ft. 

73 

1 

CO 

•^1 

1 

CO 

1 

flu 

ft< 

• 

1 

c. 

1 

In 
cop-g 

»«  1 

CO 

CO 

9^ 

a'E 

Cu 

ft. 

ft. 

ft.  So 

ft. 

1 
CO 

1 

CO 

1  i 

'    0 

1 

CO 

Oh 

1 

73 

1 

CO 

a 

ft.  Si 

T3 

^i 

CO 

1  ij 

04 

1 

c 

1 

1 
CO 

C0  + 
Oh    1 

CO 

Ch 

CU 

eu  s.^ 

0. 

b 

cu 

« 

ft.3 

o. 

flu 

O.!-, 

1  S 

CO  u 

B 

.a 

I'g 

CO  V 

eu  & 

C 

5  c 

V  rt  3 
73 

(U  2i 

.■3 

CO 

1  o 

ft.5 

a 

CO  83 
3o.l 

1 

CO 

ft. 

«| 

is 

CO  V 

ft.  So 

738  = 

1 

1 

1   * 

1 

1           . 

1        • 

rj-^* 

1 

CO 

a, 

CO 

2t 

CO 

flu 

CU 

CU 

CO  g 

curt 

ft.  >, 

CO 

CO 

CO 

CO 

0. 

CO 

cu 

73 

1 

0^ 

1 

CO 

cu 

CO  0 

1 

CO 

1 

0, 

»• 

=■^1 

"co  Jj 

a. 

73 

<A 

'Ji 

/• 

U 

ifl 

in 

Vi    S 

ffo- 

it  ^S     (JO 

i 

M 

1 

Oi 
0 

1 

wo  , 
^0.0 

0 

i4 

u 

li! 

9.- 

Kflei 

< 

2co 

i-i 

to 

ooi 

B 

Id 
H 

So 

>< 

so 

9"?. 

£b5 

i4 

X 

0 

> 

a 

0 

< 

SSz 

0 

i 

05 

u 

(!> 

to 

fa        1  U,        1  (« 

U      1  s 

2 

CO 

C-l 

n 

u 

o 

H 

•< 

"~^ 

' 

•, 

;^ 

^' 

Sd 

3- 

S  (M 

3  CO 

i^J 

•^ 

it 


I 
1 

i 

I 

3^- 


.     m  Miiirri.iVfeO'iiiw^fe 


^-i>  ■■'V- .  ■'<>.s'*;-<-"r^^.-  ■«>;-■ 


»« M»«%f  ^—- '^9'*ert*r"^  "^ 


■  t|,-,4aaei*'V5s»s»*i.^ii*- 


IIO 


TABLE  HI. 


Table  III — Continued. 


!>;i 


ill 


1! 


;i 


'1 


-I 


:  f !-' 


EXPLANATION  OF  SIGNS  AND  REMARKS  TO  THE  TABLE 

OF  SOLUBILITIES. 

(  See  pages  106-109). 


/p>  ABBREVIATIONS. 

P.— Insoluble  or  nearly  so  —  precipitated  from  highly  dilute  solution*. 

p. Slightly  soluble  —  precipitated  from  concentrated  solutions. 

S.— Soluble. 

C— Crystalline, 
am. — Ammonia, 
am.  cl. — Ammonium  chloride. 

dec. — Decomposes  in  contact  with  water. 

—.—in  dilute  acids  ( HCl  or  HNO» ). 

-|-. — in  solutions  of  the  alkalies. 

Examples:—     S 1-,  a  precipitate,  soluble  in  dilute  acids  and  alkalies: 

P  p  — , a  precipitate,  slightly  soluble  in  acids, PC h. «  crystalline  precipitate, 

Insoluble  in  acids  and  alkalies. 


NOTES. 


,    ;     '      ' '    ,  ,  ( The  numbers  refer  to  the  Table). 

/.—Double  salts  with  NaF,  KF,  and  NH«F,  are  insoluble. 

*.— Many  double  fluorides  of  Cr  with  other  bases  are  insoluble. 

J. SrCrO,  Is  soluble  in  chromic  and  other  acids. 

4. — Insoluble  in  chromic  acid. 

J.— Insoluble  in  acetic  acid. 

<j. Soluble  In  presence  of  ammonium  chloride  and  of  citrates. 

7.— The  acid  tartrate  is  sparingly  soluble. 

8. Soluble  in  presence  of  chlorides. 

9.— Readily  decomposes  into  cuprous  sulphocyanate,  which  is  colorless  and 

insoluble  in  acids, 
/o— -Soluble  in  hot^  concentrated  hydrochloric  acid.  ■*• 

//.—Soluble  in  hot  concentrated  nitric  acid. 

Ma Soluble  only  In  aqua  regia. 

/j._The  oxychlorlde,  bismuthyl  chloride,  is  Insoluble  In  water,  soluble  in  acids 
/^.— Mercurous  acetate  is  sparingly  soluble  in  water,  soluble  in  acids.   • 
/^.—Becomes  yellow  on  decomposition. 


ft.as 


T 


TABLE  IV. 


Ill 


Concentrated  Sulphuric  Add 
Dilute  Sulphuric  Add 
Concentrated  Nitric  Add 
Ordinary  Nitric  Acid 
Dilute  Nitric  Acid 
Strong  Acetic  Add 
Dilute  Acetic  Add 
Fuming  Hydrochloric  Acid 
Concentrated  Hydrochloric  Add 
Dilute  Hydrochloric  Acid 
Chlorine-water 
Bromine-water 

Aqua  Regla 


Potassium  Hydrate 
Dilute  Potassium  Hydrate 
Dilute  Sodium  Hydrate 
Concentrated  Ammonta 
Dilute  Ammonia 
Barium  Hydrate 
Caldum  Hydrate 
Ammonium  Sulphide 
Yellow  Ammonium  Sulphide 
Sodium  Phosphate 
Ammonium  Oxalate 
Sodium  Acetate 
Ammonium  Carbonate 

Potassium  Nitrite 
Potassium  Pyrochromate* 


it 


I 


I 

i,  j 

J 

f 

|i 


V.    'i 


II 


^1 


/  ita 

Table  IV — Continued. 


TABLE  IV. 


Formula  of  Reagent. 

Molecular 
Weight. 

Name. 

Number  of  drams 

in  t  Litre  of  the 

Solution. 

<NHjjjMo0.j 

196 

Ammonium  Molj'bdate 
Solution 

75 
25sc.c.Cm».HNO, 

NH4CI 

534 

Ammonium  Chloride 

>05 

K4reC,N„  3H,0 

456 

Potassium  F'errocyanide 

45-6 

KSCN 

97 

Potassium  Sulphocyanate 

97 

BaCI,,  aCjO 

344 

Barium  Chloride 

344 

Ba(NO,), 

36t 

Barium  Nitrate 

26.1 

CBSO4,  aHjO 

173 

Calcium  Sulphate 

Saturated:  about  2 

CaCI, 

III 

Calcium  Chloride 

III 

MgS04,  7H,0 

346 

Magnesium  Sulphate 

246 

MgS04,  7H,0  1 
NH4C;i         \ 

Magnesia  Mixture 

<.33 

X 105 

FeSO«,  7H,0 

278 

Ferrous  Sulphate 

278 

FeC!„  6H,0 

270 

Ferric  Chloride 

270 

re,(S04),.9H,0 

563 

Ferric  Sulphate 

281 

AgNO, 

169 

Silver  Nitrate 

16.9 

HgCl, 

271 

Mercuric  Chloride 

54-3 

SnCl,,  2H,0 

226 

Stannous  Chloride 

About  113 

PtCli.SHjO 
HjPtCl, 

480 

Platinum  Chloride,  or 
Chloroplatinic  Acid 

96 

Co(NO,)„  sH,0 

27a 

Cobaltous  Nitrate 

87.2 

KOH  ) 

KI 
HgCl,) 

Nessler's  Reagent* 

( 150 

63-5 
{About  31.2 

■In  preparing  Nessler's  reagent,  the  potassium  iodide  and  the  mercuric  chloride  are  to  be 
separately  dissolved;  the  former  in  iooc.c.,'the  latter  in  about  800  c.c.  of  water,  with  the 
aid  of  heat.  When  cold,  add  the  second  solution  to  the  first,  with  constant  stirring,  until  a 
permanent  precipitate  begins  to  form,  then  add  the  potassium  hydrate,  and  malie  up  to  i  litre. 

After  standing  for  some  time,  the  clear  portion  of  the  solution  is  to  be  drawn  off  for  use. 


fiii 


'■'■mimmmmmifiim 


wm 


mum 


T 


Acetates.  63, 20,  3i,  2$. 
ArW-  Hectic.  A.2.  63.  7«. 


INDEX. 


Add,  sulphurous,  4:.  44i  ^V* 

__     tartarlr    it'- ft'-  — 


ERRATA. 

p.  as;  fourth  Hne  fron,  bottom,  lor  "ammonium"  ^-^  "f  >«™ " 

:.39;  marginal  "-' »- "-^"^^C:!:  '  carS"  the  wo^s.  "with 
p.  66;  seventeenth  Hne  from  bottom,  tnsert  alter 
»odlum  carbonate." 


__    nitrous,  54. 

__    orthophosphoric,  43,  48.  83. 

—    oxalic,  43, 46- 

removal  of,  80. 

_    permanganic,  36. 

_    pru8»ic,43.6i.73-  «„  „, 

_    L    detection  of  inorganic  matter,9i 

Acids,  classification  of,  43. 

_    detection  of,  68. 
Acid,  silicic,  43.  SI.  52.  7'.  89- 

__    sulphocyanic,  43.  53.  7*- 

_    Buiphuric,  43, 43.  7o- 

__    _    test  by  means  of,  67, 68. 


Basic  acetate  method  for  the  separation  of 

phosphoric  acid,  etc.,  83- 
Basic  acetates,  20,  si,  3$. 
Bicarbonates,  46. 

_    of  calcium  and  magnesium,  93- 
Bismuth,  reactions  of,  32. 

_    detection  of,  79-  ' 

Bismuthyl,  33- 

Blowpipe,  toble  for  er.amination  by,  105. 

use  of  the,  4. 

Blue  glass,  use  of,  14. 
_-    paper,  24. 

'^  113 


I 


I J 


?  ■ 


r 
I     ^ 

fl 

« .1 


yi 

■     *r 

-  I 
1 1 


"1 


xia 

Tablr  IV — CoMlinued. 


TABLE  IV. 


Formula  of  Reagent. 


(NH^MoO,j 

NH4CI 

K«FeC»N*,  3H,0 

KSCN 

BaCli,  aCjO 

Ba(NO,), 
CaSO«,  aHaO 

.    c«ci, 

MgS04,  7H,« 

MgS04,  7H,< 
NH4CI 

FeSOi,  7H,( 

FeCl,,  6H,0 

Fe,(S04)„  9H, 

AgNO, 

HgCl, 

SnCI,,  3H,0 

PtCh,  8HgO 
HgPtCU 

Co(NO,)„  sH, 


Molecular 
Weight. 


KOH 

KI 

HgCl 


J 


*In  preparing  1 
separately  dissoli 
aid  of  heat.     Wh 


196 

SM 
456 

97 
'44 
]6i 

173 


Name. 


Ammonium  Molybdate 
Solution 

Ammonium  Chloride 

Potassium  Ferrocyanide 

Potassium  Sulphocyanate 

Barium  Chloride 

Barium  Nitrate 

Calcium  Siilnhatw 


Number  of  drama 

iM  /  Litre  of  the 

Solution. 


75 
aSScc.Cwi.HNO, 

«o5 

45-6 

97 

36.1 


permanent  precipitate  begins  to  form,  then  add  the  potassium  hydrate,  and  make  up  to  i  litre. 
After  standing  for  some  time,  the  clear  portion  of  the  solution  is  \o  be  drawn  off  for  use. 


''^Nf^««;s»<!i(M^fMkH«si^i«t«#us; 


I.- 


T 


INDEX. 


drate,  and  make  up  to  i  litre. 
)n  is  io  be  drawn  off  for  use. 


Acetates,  63, 20,  ai,  25. 
Stic,  43. 62,  75- 
timonous,  39. 
inlc,  36.  37.  49.  78. 4^.  7>- 
inous,  36,  37. 
Ic,  43,  SO.  7»- 
rbonic,  43,  4S.  7°- 
lorlc,  43, 63,  75- 
oroplatinic,  40. 
Wous,  43,  55.  72' 
>mic,  43,  50,  70- 
lUlclc,  53. 
Jriodic,  43.  59- 
Idrobromic,  43.  59- 
drochloric,  43.  S^- 
idrocyanic,  43, 61, 73. 
jdroferricyanic,  53,  54- 
,  Wroferrocyanic,  53. 
«dfofluoric,  43, 47. 
jhlorous,  55. 
intimonlc,  39.  78- 
.tannic,  35.  78, 88,  89. 
^  Ic,  43, 63,  75. 

—  Tfltrous,  54. 

—  orthophosphoric,  43, 48, 83. 

_    oxalic,  43, 46. 

removal  of,  8q. 

permanganic,  36. 

—  prussic,  43. 6'.  73- 
_    _    detection  of  inorganic  matter, 91 

Acids,  classification  of,  43. 

__    detection  of,  68. 
Acid,  sUiclc,  43.  S».  52.  7'.  89- 

—  sulphocyanlc,  43,  53. 1*' 

—  sulphuric,  43, 43.  70- 
__    test  by  means  of,  67, 68. 


Acid,  sulphurous,  43. 44,  67. 

—  urtarlc,  43. 6«. 

Alcohol,  used  as  a  test  for  borates,  50.  S'- 
Alkalies,  9,  13. 

—  detection  of  in  silicates,  89. 
Alkaline  earths,  metals  of  the,  1 5- 
Alloys,  analysis  of,  loi. 

_    blowpipe  examination  of,  104. 
Aluminium,  19,  83,  84. 

—    oxide,  90. 
Ammonia,  14,  86. 

_    detecUon  of  In  potable  water,  95,  97 

Anhydrides,  34. 
Antimony,  38,  39.  78- 
Aqua  regia,  86. 
Arsenates,  42,  49,  7i' 
Arsenic,  36.  37.  49.  7».  78- 
Ash,  analysis  of,  87. 
Atomic  weights,  103. 

Barium,  17, 85. 

—    sulphate,  87. 
Bases,  classification  of,  n- 

_    separation  into  groups,  75.  76. 
Basic  acetate  method  for  the  separation  of 

phosphoric  acid,  etc.,  83. 
Basic  acetates,  20,  3i,  35. 
Bicarbonates,  46. 

_    of  calcium  and  magnesium,  93. 
Bismuth,  reactions  of,  32. 
_    detection  of,  79. 

Bismuthyl,  33. 

Blowpipe,  table  for  examinaUon  by,  105. 

—    use  of  the,  4. 
Blue  glass,  use  of,  14. 

_    paper,  24. 

U3 


M' 


i7%. 


• — ssnw 


"■"Mp***"*^' 


.V. 


'■^MHMI 

HHHHI 

.    t^ 

114 

INDEX.                                                                         1 

Blue  paper,  a*  test  for  iiilphurou*  acid,  45. 

Ferrous  salts,  23. 

Boilers,  corrosion  of,  100. 

Films,  5,  36,  39,  33.  33.  36.  38. 

Boiler  scale,  100. 

' 

Filtration,  8. 

i  : 

Borates,  42,50,  71. 

Flame  tests,  65. 

Borax  tiead,  4. 

Fluorides,  reactions  of,  47. 

Broiiiides,  43,  59,  73. 

—    detection  of,  68. 

Bromine,  free,  56. 

—    removal  of,  83. 

Bunsen  flame,  a. 

Fluor-spar,  48. 

• 

Cadmium,  reactions  of,  33. 

Gold,  40,  78. 

—    detection  of,  80. 

Griess's  test,  99. 

—    separation  of  from  copper. 

34- 

Haloids,  55,  73. 
Haloid  salu,  73. 

Calcium,  reactions  of,  16. 

—    detection  of,  85. 

Hard:iess  of  water,  93. 

i 

—    sulphate,  as  reagent,  84. 
Carbon,  87. 

Heavy  metals,  37. 
Hypochlorite*,  43,  5S.  72- 

Carbonates,  43,  45,  70. 

■i 

Chlorates,  43,  63,  75. 

Insoluble  compounds,  86. 

I' 

Chlorides,  43,  58,  59.  74- 

Iodides,  43,  59,  60. 

1     ■ 

—    in  sewage,  93. 

—    detection  of  in  mixtures,  73. 

—    detection  of  in  water,  94. 

Iodine,  free,  56,  57. 

K  ^ 

Chlorine,  free,  55. 

Iron,  reactions  of,  23. 

#  ;■ 

Chlorites,  43,  55,  72. 

—    detection  of,  82. 

Chloroplatinates,  13,  15,  40. 

Lacmoid  paper,  10, 

Chromates,  43,  50,  70. 

Lead,  reactions  of,  29. 

Chromium,  83,  84. 

—    detection  of,  79. 

V"      i 

—    oxide,  90. 

—    —    in  well-water,  93,  96. 

—    salts  of,  30. 

—    chromate,  30. 

1 

—    —    conversion  into  chromic  acid,  2 1 

—    paper,  57. 

Chromyl  chloride,  59,  74. 

—    sulphate,  30,  88. 

Cobalt,  reactions  of,  31. 

ri 

—    detection  of,  81. 

Magnesium  ammonium  phosphite,  18. 

—    sol  ution,  as  reagent,  1 8, 1 9 

36, 35.  >05 

—    reactions  of,  17. 

Contamination  of  potable  waters 

.93.99.100 

—    detection  of,  84. 

Copper,  reactions  of,  31. 

—    —    In  water,  94. 

; 

—    detection  of,  79. 

Manganese,  reactions  of,  25. 

Cream  of  tartar,  14,  61. 

—    detection  of,  83. 

Cuprous  iodide,  31. 

Marsh's  test  for  arsenic,  38. 

—     sulphocyanate,  31. 

Matrass,  the,  5,  6, 66. 

Cyanides,  compound,  73,  90,  53,  54. 

Mercurous  salts,  28.      *" 

-.    i 

—    simple,  43,  61,  73,  74. 

Mercuric  salts,  29. 

5       Jf       ■■■; 

—    —    detection  in  organic  1 

natter,  91. 

Mercury,  28,  79. 

Cyanide  flux,  5,  36,  105. 

Metals,  reducible,  67. 

Eler    nts,  the,  103. 

Metantimonic  acid — see  antimony. 
MeUphosphate  bead,  4,  52. 

Evaporation,  9. 

Metastannic  acid—  see  tin. 

Ferric  salts,  34. 

Microcosmlc  salt,  4. 

•     A 

Ferrlcyanides,  43,  53,  54,  72. 

Micro-organisms  in  water,  99. 

^:i, 

Fcrrocyanldes,  43,  53,  73. 

Mirror,  arsenical,  38. 

I..- 


33.  36.  38. 


o'.47. 


93. 

55.  7a- 
Inds,  86. 

If  in  mixtures,  73. 

1.33. 
)f,  83. 


[O. 

>f,  29. 
of,  79. 

|ll-watcr,  93,  96. 
,30- 


30,88. 

nonium  phosphate,  18. 

of,  17. 

of,  84. 

Iter,  94. 

:tions  of,  35. 

of,  82. 

-  arsenic,  38. 

6,66. 

,38,      "^ 

I9- 

e,  67. 

:{d — see  antimony. 

bead,  4,  53. 

1—  see  tin. 

'.4- 

>  in  water,  99. 

1.38. 


INDEX. 


1x5 


Molybdate  test  for  phosphoric  acid,  48. 

Nessler's  reagent,  15,  95,  97,  1 13. 
Niclcel,  reactions  of,  33. 

—  detection  of,  81. 

—  separation  of,  from  cobalt,  83. 
Nitrates,  43,  63,  63,  75. 

—  'n  drinlcing-water,  95,  96. 
Nitrites,  43,  54,  73. 

—  detection  of,  in  water,  95,  98. 

Open  tul>e,  the,  7. 

Organic  matter,  removal  of,  90- 

—  —    detection  of  in  water,  95, 98. 
Oxalates,  43, 46. 

—  removal  of,  8a 
Oxidizing  flame,  3,  4. 

Phosphates,  43,  48. 

—  removal  of,  83. 

—  detection  of,  in  water,  93,  96. 
Platinum,  40,  78. 

—  detection  of,  in  allojrs,  loi. 
Poisons,  detection  of,  in  organic  matter,  91. 
Polysulphldes.  43,  57,  58,  72. 
Potassium,  13. 

—  detection  of,  86. 

—  —    in  potable  water,  97. 
Precipitation,  8.  , 
Prussian  blue,  34,  53. 

Purple  of  Cassius,  41. 

Quantivalence  of  the  elements,  103. 

Reaction,  acid,  alkaline,  9, 10. 

Reactions,  i. 

Reagents,  definition  of,  3. 

—  table  of.  III. 
Reducing  flame,  3,  4. 
Reduction  on  charcoal,  5,  36,  66,  67. 
Relnsch's  test  for  arsenic,  37. 

Sewage,  100.  r. 

Silicates,  43,  51,  52,  71. 

—  analysis  of,  89. 


Silver,  37,  79. 

—  bromide,  chloride  and  iodide,  88. 
Soda  bead,  4,  53. 

Sodium,  13,  86. 

—  detection  of,  in  water,  97. 
Solubilities,  table  of,  106  -  no. 
Solubility,  7. 

Stannic  compound^  35. 

—  oxide,  88. 
Stannous)  compounds,  35. 
Strontium,  reactions  of,  16. 

—  detection  of,  85. 

—  sulphate,  87. 

—  -  -    separation  from  the  sulphates  of 

barium  and  lead,  88. 
Sulphates,  43,  43,  70,  88,  89. 
Sulphides,  43,  57,  73,  74. 
Sulphites,  43,  44,  67. 
Sulphocyanates,  43,  53,  72. 
Sulphur,  87. 

—  detection  of,  66. 

—  compounds,  test  for,  44. 

Tartrates,  43,  61,  63,  74. 
Test  paper,  9,  34,  45,  57. 
Thiosulphates,  43,  58,  73,  73, 
Tin,  34,  35. 

—  oxides  and  acids  of,  78,  88,  89. 

—  reduction  of,  36. 
Turmeric  paper,  9. 

—  deportment  toward  carbonates,  46. 

—  as  test  for  boric  acid,  51. 
Turnbuli's  blue,  33,  54. 

Washing  of  precipitates,  8. 
Water,  analysis  of,  93. 

—  detection  of,  6. 

Xanthoproteic  reaction,  63. 

Zambelll's  reaction  for  nitrites,  55, 98. 
Zinc,  reactions  of,  26. 

—  detection  of,  83. 


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